Method and apparatus for inspection

ABSTRACT

An electron beam inspection apparatus, the apparatus including a plurality of electron beam columns, each electron beam column configured to provide an electron beam and detect scattered or secondary electrons from an object, and an actuator system configured to move one or more of the electron beam columns relative to another one or more of the electron beam columns, the actuator system including a plurality of first movable structures at least partly overlapping a plurality of second movable structures, the first and second movable structures supporting the plurality of electron beam columns.

This application is a continuation of U.S. patent application Ser. No.16/064,193, filed on Jun. 20, 2018, now allowed, which is the U.S.national phase entry of PCT Patent Application No. PCT/EP2016/080374,filed on Dec. 9, 2016, which claims the benefit of priority of EuropeanPatent Application No. 15202676.1, filed on Dec. 24, 2015, and ofEuropean Patent Application No. 16166550.0, filed on Apr. 22, 2016, eachof the foregoing applications is incorporated herein in its entirety byreference.

FIELD

The present description relates to methods and apparatus for inspection.

BACKGROUND

A lithographic apparatus is a machine that applies a desired patternonto a substrate, usually onto a target portion of the substrate. Alithographic apparatus can be used, for example, in the manufacture ofintegrated circuits (ICs). In that instance, a patterning device, whichis alternatively referred to as a mask or a reticle, may be used togenerate a circuit pattern to be formed on an individual layer of theIC. This pattern can be transferred onto a target portion (e.g.,including part of, one, or several dies) on a substrate (e.g., a siliconwafer). Transfer of the pattern is typically via imaging onto a layer ofradiation-sensitive material (resist) provided on the substrate. Ingeneral, a single substrate will contain a network of adjacent targetportions that are successively patterned. Known lithographic apparatusinclude so-called steppers, in which each target portion is irradiatedby exposing an entire pattern onto the target portion at one time, andso-called scanners, in which each target portion is irradiated byscanning the pattern through a radiation beam in a given direction (the“scanning”-direction) while synchronously scanning the substrateparallel or anti parallel to this direction. It is also possible totransfer the pattern from the patterning device to the substrate byimprinting the pattern onto the substrate.

SUMMARY

Manufacturing devices, such as semiconductor devices, typically involvesprocessing a substrate (e.g., a semiconductor wafer) using a number offabrication processes to form various features and multiple layers ofthe devices. Such layers and features are typically manufactured andprocessed using, e.g., deposition, lithography, etch,chemical-mechanical polishing, and ion implantation. Multiple devicesmay be fabricated on a plurality of dies on a substrate and thenseparated into individual devices. This device manufacturing process maybe considered a patterning process. A patterning process involves apatterning step, such as optical and/or nanoimprint lithography using alithographic apparatus, to provide a pattern on a substrate andtypically, but optionally, involves one or more related patternprocessing steps, such as resist development by a development apparatus,baking of the substrate using a bake tool, etching using the patternusing an etch apparatus, etc. Further, one or more metrology processesare typically involved in the patterning process.

Metrology processes are used at various stages of a patterning processto setup, monitor and/or control the process. For example, metrologyprocesses are used to measure one or more characteristics of asubstrate, such as a relative location (e.g., registration, overlay,alignment, etc.) or dimension (e.g., line width, critical dimension(CD), thickness, etc.) of features formed on the substrate during thepatterning process, and/or of a patterning device (e.g., a reticle),such as relative location (e.g., registration error) or dimension (e.g.,line width, critical dimension (CD), etc.) Using the one or morecharacteristics, the setup, performance, etc. of the patterning processcan be determined. If the one or more characteristics are unacceptable(e.g., out of a predetermined range for the characteristic(s)), themeasurements of the one or more characteristics may be used to alter oneor more parameters of the patterning process such that substratesmanufactured by the patterning process have an acceptablecharacteristic(s).

With the advancement of lithography and other patterning processtechnologies, the dimensions of functional elements have continuallybeen reduced while the amount of the functional elements, such astransistors, per device has been steadily increased over decades. In themeanwhile, the requirement of accuracy in terms of overlay, criticaldimension (CD), etc. has become more and more stringent. Errors, such asoverlay errors, CD errors, registration errors, etc., will inevitably beproduced as part of the overall patterning process. For example, imagingerrors may be produced from optical aberration, patterning deviceheating, patterning device errors, and/or substrate heating and can becharacterized in terms of, e.g., overlay errors, CD errors, etc.Additionally or alternatively, errors may be introduced in other partsof the patterning process, such as in the patterning device, by an etchprocess, by a development process, by a bake process, etc. and similarlycan be characterized in terms of parameters such as registration error,overlay error, CD error, etc. The errors may directly cause a problem interms of the function of the device, including failure of the device tofunction or one or more electrical problems of the functioning device.

As noted above, in patterning processes, it is desirable to frequentlymake measurements of the structures used or created, e.g., for processcontrol and verification. One or more parameters of the structures aretypically measured or determined, for example the critical dimension ofa structure, the overlay error between successive layers formed in or ona substrate, etc. There are various techniques for making measurementsof the microscopic structures used or formed in a patterning process.Various tools for making such measurements are known including, but notlimited to, scanning electron microscopes (SEMs), which are often usedto measure critical dimension (CD). SEMs have high resolving power andare capable of resolving features of the order of 30 nm or less, 20 nmor less, 10 nm or less, or 5 nm or less. SEM images of semiconductordevices are often used in the semiconductor fab to observe what ishappening at the device level.

The information contained in SEM images of structures can be used forprocess modeling, existing model calibration (including recalibration),defect detection, estimation, characterization or classification, yieldestimation, process control or monitoring, etc. Such SEM images may beprocessed to extract contours that describe the edges of objects,representing device structures (whether on a patterning device or formedon a substrate), in the image. These contours are then quantified viametrics, such as CD, at user-defined cut-lines. Thus, typically, theimages of device structures are compared and quantified via metrics,such as an edge-to-edge distance (CD) measured on extracted contours orsimple pixel differences between images.

In an embodiment, there is provided an electron beam inspectionapparatus to inspect an object comprising a plurality of dies or fields,the apparatus comprising: a plurality of electron beam columns, eachelectron beam column configured to provide an electron beam and detectscattered or secondary electrons from the object, each electron beamcolumn arranged to inspect a different respective field or dieassociated with the electron beam column; and a non-transitory computerprogram product comprising machine-readable instructions, at least someof the instructions configured to cause relative movement between theobject and the electron beam columns such that each of the electronbeams inspects an area of its respective field or die less than theentire area of the respective field or die.

In an embodiment, there is provided an electron beam inspectionapparatus, comprising: a plurality of electron beam columns, eachelectron beam column configured to provide an electron beam and detectscattered or secondary electrons from the object, each electron beamcolumn arranged to inspect an area of a different respective field ordie associated with the electron beam column; and an actuator systemconfigured to move one or more of the electron beam columns relative toanother one or more of the electron beam columns.

In an embodiment, there is provided a method of electron beam inspectionof an object comprising a plurality of dies or fields, the methodcomprising: having a plurality of electron beam columns, each electronbeam column configured to provide an electron beam and detect scatteredor secondary electrons from the object and each electron beam columnarranged to inspect a different respective field or die associated withthe electron beam column; causing relative movement between the objectand the plurality of electron beam columns such that each of theelectron beams inspects an area of its respective field or die less thanthe entire area of the respective field or die; providing the electronbeams onto the object from the electron beam columns; and detectingscattered or secondary electrons from the object using the electron beamcolumns.

In an embodiment, there is provided a method of electron beaminspection, the method comprising: having a plurality of electron beamcolumns, each electron beam column configured to provide an electronbeam and detect scattered or secondary electrons from an object and eachelectron beam column arranged to inspect an area of a differentrespective field or die associated with the electron beam column; andmoving one or more of the electron beam columns relative to another oneor more of the electron beam columns using an actuator system.

In an aspect, there is provided a method of manufacturing deviceswherein a device pattern is applied to a series of substrates using apatterning process, the method including evaluating a patternedstructure formed using the patterning process using a method describedherein and controlling the patterning process for one or more of thesubstrates in accordance with the result of the method. In anembodiment, the patterned structure is formed on at least one of thesubstrates and the method comprises controlling the patterning processfor later substrates in accordance with the result of the method.

In aspect, there is provided a non-transitory computer program productcomprising machine-readable instructions configured to cause a processorto cause performance of a method described herein.

In an aspect, there is provided an electron beam inspection system. Thesystem includes an electron beam inspection apparatus as describedherein; and an analysis engine comprising a non-transitory computerprogram product as described herein. In an embodiment, the systemfurther comprises a lithographic apparatus comprising a supportstructure configured to hold a patterning device to modulate a radiationbeam and a projection optical system arranged to project the modulatedradiation beam onto a radiation-sensitive substrate.

In an embodiment, there is provided an electron beam inspectionapparatus, the apparatus comprising: a plurality of electron beamcolumns, each electron beam column configured to provide an electronbeam and detect scattered or secondary electrons from an object; and anactuator system configured to move one or more of the electron beamcolumns relative to another one or more of the electron beam columns,the actuator system comprising a plurality of first movable structuresat least partly overlapping a plurality of second movable structures,the first and second movable structures supporting the plurality ofelectron beam columns.

In an embodiment, there is provided a method of electron beaminspection, the method comprising: having a plurality of electron beamcolumns, each electron beam column configured to provide an electronbeam and detect scattered or secondary electrons from an object; movingone or more of the electron beam columns relative to another one or moreof the electron beam columns using an actuator system, the actuatorsystem comprising a plurality of first movable structures at leastpartly overlapping a plurality of second movable structures, the firstand second movable structures supporting the plurality of electron beamcolumns; providing the electron beams onto the object from the electronbeam columns; and detecting scattered or secondary electrons from theobject using the electron beam columns.

In an embodiment, there is provided a patterning device repairapparatus, comprising: a plurality of beam columns, each beam columnconfigured to provide a beam of radiation, each beam column arranged torepair an area of a different respective field or die of a patterningdevice associated with the beam column using the respective beam ofradiation; and an actuator system configured to move one or more of thebeam columns relative to another one or more of the beam columns.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, withreference to the accompanying drawings in which:

FIG. 1 schematically depicts an embodiment of a lithographic apparatus;

FIG. 2 schematically depicts an embodiment of a lithographic cell orcluster;

FIG. 3 schematically depicts an embodiment of a scanning electronmicroscope (SEM);

FIG. 4 schematically depicts an embodiment of multi-beam electron beamprocessing of an object;

FIG. 5 schematically depicts an embodiment of multi-column electron beamprocessing of an object;

FIG. 6 schematically depicts a top or bottom view of an embodiment of amulti-column electron beam apparatus;

FIG. 7 schematically depicts a perspective view of an embodiment of amulti-column electron beam apparatus;

FIG. 8 schematically depicts a side view of an embodiment of a column ofa multi-column electron beam apparatus;

FIG. 9 schematically depicts a top or bottom view of an embodiment of acolumn of a multi-column electron beam apparatus;

FIG. 10 schematically depicts an embodiment of adjustment of certaincolumns of a multi-column electron beam apparatus;

FIGS. 11A, 11B and 11C schematically depict an embodiment of a method ofprocessing an object to identify defects;

FIGS. 12A and 12B schematically depict an embodiment of a method ofprocessing an object to identify defects;

FIG. 13 depicts an example flow chart for modeling and/or simulatinglithography in a lithographic projection apparatus;

FIG. 14 schematically depicts a top or bottom view of an embodiment of amulti-column electron beam apparatus;

FIG. 15 schematically depicts a side view of an embodiment of a columnof a multi-column electron beam apparatus;

FIGS. 16A and 16B schematically depict a top or bottom view of anembodiment of a multi-column electron beam apparatus; and

FIGS. 17A and 17B schematically depict a side view of an embodiment of acolumn of a multi-column electron beam apparatus.

DETAILED DESCRIPTION

Before describing embodiments in detail, it is instructive to present anexample environment in which embodiments may be implemented.

FIG. 1 schematically depicts a lithographic apparatus LA. The apparatuscomprises:

an illumination system (illuminator) IL configured to condition aradiation beam B (e.g. DUV radiation or EUV radiation);

a support structure (e.g. a mask table) MT constructed to support apatterning device (e.g. a mask) MA and connected to a first positionerPM configured to accurately position the patterning device in accordancewith certain parameters;

a substrate table (e.g. a wafer table) WTa constructed to hold asubstrate (e.g. a resist-coated wafer) W and connected to a secondpositioner PW configured to accurately position the substrate inaccordance with certain parameters; and

a projection system (e.g. a refractive projection lens system) PSconfigured to project a pattern imparted to the radiation beam B bypatterning device MA onto a target portion C (e.g. comprising one ormore dies) of the substrate W.

The illumination system may include various types of optical components,such as refractive, reflective, magnetic, electromagnetic, electrostaticor other types of optical components, or any combination thereof, fordirecting, shaping, or controlling radiation.

The patterning device support structure holds the patterning device in amanner that depends on the orientation of the patterning device, thedesign of the lithographic apparatus, and other conditions, such as forexample whether or not the patterning device is held in a vacuumenvironment. The patterning device support structure can use mechanical,vacuum, electrostatic or other clamping techniques to hold thepatterning device. The patterning device support structure may be aframe or a table, for example, which may be fixed or movable asrequired. The patterning device support structure may ensure that thepatterning device is at a desired position, for example with respect tothe projection system. Any use of the terms “reticle” or “mask” hereinmay be considered synonymous with the more general term “patterningdevice.”

The term “patterning device” used herein should be broadly interpretedas referring to any device that can be used to impart a radiation beamwith a pattern in its cross-section such as to create a pattern in atarget portion of the substrate. It should be noted that the patternimparted to the radiation beam may not exactly correspond to the desiredpattern in the target portion of the substrate, for example if thepattern includes phase-shifting features or so called assist features.Generally, the pattern imparted to the radiation beam will correspond toa particular functional layer in a device being created in the targetportion, such as an integrated circuit.

The patterning device may be transmissive or reflective. Examples ofpatterning devices include masks, programmable mirror arrays, andprogrammable LCD panels. Masks are well known in lithography, andinclude mask types such as binary, alternating phase-shift, andattenuated phase-shift, as well as various hybrid mask types. An exampleof a programmable mirror array employs a matrix arrangement of smallmirrors, each of which can be individually tilted so as to reflect anincoming radiation beam in different directions. The tilted mirrorsimpart a pattern in a radiation beam, which is reflected by the mirrormatrix.

The term “projection system” used herein should be broadly interpretedas encompassing any type of projection system, including refractive,reflective, catadioptric, magnetic, electromagnetic and electrostaticoptical systems, or any combination thereof, as appropriate for theexposure radiation being used, or for other factors such as the use ofan immersion liquid or the use of a vacuum. Any use of the term“projection lens” herein may be considered as synonymous with the moregeneral term “projection system”.

As here depicted, the apparatus is of a transmissive type (e.g.,employing a transmissive mask). Alternatively, the apparatus may be of areflective type (e.g., employing a programmable mirror array of a typeas referred to above, or employing a reflective mask).

The lithographic apparatus may be of a type having two (dual stage) ormore tables (e.g., two or more substrate table, two or more patterningdevice support structures, or a substrate table and metrology table). Insuch “multiple stage” machines the additional tables may be used inparallel, or preparatory steps may be carried out on one or more tableswhile one or more other tables are being used for pattern transfer.

The lithographic apparatus may also be of a type wherein at least aportion of the substrate may be covered by a liquid having a relativelyhigh refractive index, e.g., water, so as to fill a space between theprojection system and the substrate. An immersion liquid may also beapplied to other spaces in the lithographic apparatus, for example,between the mask and the projection system. Immersion techniques arewell known in the art for increasing the numerical aperture ofprojection systems. The term “immersion” as used herein does not meanthat a structure, such as a substrate, must be submerged in liquid, butrather only means that liquid is located between the projection systemand the substrate during exposure.

Referring to FIG. 1, the illuminator IL receives a radiation beam from aradiation source SO. The source and the lithographic apparatus may beseparate entities, for example when the source is an excimer laser. Insuch cases, the source is not considered to form part of thelithographic apparatus and the radiation beam is passed from the sourceSO to the illuminator IL with the aid of a beam delivery system BDincluding, for example, suitable directing mirrors and/or a beamexpander. In other cases the source may be an integral part of thelithographic apparatus, for example when the source is a mercury lamp.The source SO and the illuminator IL, together with the beam deliverysystem BD if required, may be referred to as a radiation system.

The illuminator IL may include an adjuster AD for adjusting the angularintensity distribution of the radiation beam. Generally, at least theouter and/or inner radial extent (commonly referred to as σ-outer andσ-inner, respectively) of the intensity distribution in a pupil plane ofthe illuminator can be adjusted. In addition, the illuminator IL mayinclude various other components, such as an integrator IN and acondenser CO. The illuminator may be used to condition the radiationbeam, to have a desired uniformity and intensity distribution in itscross section.

The radiation beam B is incident on the patterning device (e.g., mask)MA, which is held on the patterning device support (e.g., mask tableMT), and is patterned by the patterning device. Having traversed thepatterning device (e.g., mask) MA, the radiation beam B passes throughthe projection system PS, which focuses the beam onto a target portion Cof the substrate W. With the aid of the second positioner PW andposition sensor IF (e.g., an interferometric device, linear encoder, 2-Dencoder or capacitive sensor), the substrate table WTa can be movedaccurately, e.g., so as to position different target portions C in thepath of the radiation beam B. Similarly, the first positioner PM andanother position sensor (which is not explicitly depicted in FIG. 1) canbe used to accurately position the patterning device (e.g., mask) MAwith respect to the path of the radiation beam B, e.g., after mechanicalretrieval from a mask library, or during a scan. In general, movement ofthe patterning device support (e.g., mask table) MT may be realized withthe aid of a long-stroke module (coarse positioning) and a short-strokemodule (fine positioning), which form part of the first positioner PM.Similarly, movement of the substrate table WTa may be realized using along-stroke module and a short-stroke module, which form part of thesecond positioner PW. In the case of a stepper (as opposed to a scanner)the patterning device support (e.g., mask table) MT may be connected toa short-stroke actuator only, or may be fixed.

Patterning device (e.g., mask) MA and substrate W may be aligned usingmask alignment marks M1, M2 and substrate alignment marks P1, P2.Although the substrate alignment marks as illustrated occupy dedicatedtarget portions, they may be located in spaces between target portions(these are known as scribe-lane alignment marks). Similarly, insituations in which more than one die is provided on the patterningdevice (e.g., mask) MA, the mask alignment marks may be located betweenthe dies. Small alignment markers may also be included within dies, inamongst the device features, in which case it is desirable that themarkers be as small as possible and not require any different patterningor other process conditions than adjacent features. An embodiment of analignment system, which detects the alignment markers, is describedfurther below.

The depicted apparatus could be used in at least one of the followingmodes:

In step mode, the patterning device support (e.g., mask table) MT andthe substrate table WTa are kept essentially stationary, while an entirepattern imparted to the radiation beam is projected onto a targetportion C at one time (i.e., a single static exposure). The substratetable WTa is then shifted in the X and/or Y direction so that adifferent target portion C can be exposed. In step mode, the maximumsize of the exposure field limits the size of the target portion Cimaged in a single static exposure.

In scan mode, the patterning device support (e.g., mask table) MT andthe substrate table WTa are scanned synchronously while a patternimparted to the radiation beam is projected onto a target portion C(i.e., a single dynamic exposure). The velocity and direction of thesubstrate table WTa relative to the patterning device support (e.g.,mask table) MT may be determined by the (de-)magnification and imagereversal characteristics of the projection system PS. In scan mode, themaximum size of the exposure field limits the width (in the non-scanningdirection) of the target portion in a single dynamic exposure, whereasthe length of the scanning motion determines the height (in the scanningdirection) of the target portion.

In another mode, the patterning device support (e.g., mask table) MT iskept essentially stationary holding a programmable patterning device,and the substrate table WTa is moved or scanned while a pattern impartedto the radiation beam is projected onto a target portion C. In thismode, generally a pulsed radiation source is employed and theprogrammable patterning device is updated as required after eachmovement of the substrate table WTa or in between successive radiationpulses during a scan. This mode of operation can be readily applied tomaskless lithography that utilizes programmable patterning device, suchas a programmable mirror array of a type as referred to above.

Combinations and/or variations on the above described modes of use orentirely different modes of use may also be employed.

Lithographic apparatus LA is of a so-called dual stage type which hastwo tables WTa, WTb (e.g., two substrate tables) and two stations—anexposure station and a measurement station—between which the tables canbe exchanged. For example, while a substrate on one table is beingexposed at the exposure station, another substrate can be loaded ontothe other substrate table at the measurement station and variouspreparatory steps carried out. The preparatory steps may include mappingthe surface control of the substrate using a level sensor LS andmeasuring the position of alignment markers on the substrate using analignment sensor AS, both sensors being supported by a reference frameRF. If the position sensor IF is not capable of measuring the positionof a table while it is at the measurement station as well as at theexposure station, a second position sensor may be provided to enable thepositions of the table to be tracked at both stations. As anotherexample, while a substrate on one table is being exposed at the exposurestation, another table without a substrate waits at the measurementstation (where optionally measurement activity may occur). This othertable has one or more measurement devices and may optionally have othertools (e.g., cleaning apparatus). When the substrate has completedexposure, the table without a substrate moves to the exposure station toperform, e.g., measurements and the table with the substrate moves to alocation (e.g., the measurement station) where the substrate is unloadedand another substrate is load. These multi-table arrangements enable asubstantial increase in the throughput of the apparatus.

As shown in FIG. 2, a lithographic apparatus LA may form part of alithographic cell LC, also sometimes referred to as a lithocell orlithocluster, which also includes apparatus to perform one or more pre-and post-pattern transfer processes on a substrate. Conventionally theseinclude one or more spin coaters SC to deposit a resist layer, one ormore developers DE to develop patterned resist, one or more chill platesCH and one or more bake plates BK. A substrate handler, or robot, ROpicks up a substrate from input/output ports I/O1, I/O2, moves itbetween the different process devices and delivers it to the loading bayLB of the lithographic apparatus. These devices, which are oftencollectively referred to as the track, are under the control of a trackcontrol unit TCU which is itself controlled by the supervisory controlsystem SCS, which also controls the lithographic apparatus vialithographic control unit LACU. Thus, the different apparatus may beoperated to maximize throughput and processing efficiency.

Further, it is often desirable to model the patterning process so that,for example, the patterning process can be designed, controlled,monitored, etc. Thus, one or more mathematical models can be providedthat describe one or more steps of the patterning process, includingtypically the pattern transfer step. In an embodiment, a simulation ofthe patterning process can be performed using one or more mathematicalmodels to simulate how the patterning process forms a patternedsubstrate using a measured or design pattern provided by a patterningdevice. An exemplary flow chart for modeling and/or simulatinglithography in a lithographic projection apparatus is illustrated inFIG. 13. As will be appreciated, the models may represent a differentpatterning process and need not comprise all the models described below.A source model 1300 represents optical characteristics (includingradiation intensity distribution, bandwidth and/or phase distribution)of the illumination of a patterning device. The source model 1300 canrepresent the optical characteristics of the illumination that include,but not limited to, numerical aperture settings, illumination sigma (a)settings as well as any particular illumination shape (e.g. off-axisradiation shape such as annular, quadrupole, dipole, etc.). A projectionoptics model 1310 represents optical characteristics (including changesto the radiation intensity distribution and/or the phase distributioncaused by the projection optics) of the projection optics. Theprojection optics model 1310 can represent the optical characteristicsof the projection optics, including aberration, distortion, one or morerefractive indexes, one or more physical sizes, one or more physicaldimensions, etc. A design layout model 1320 represents opticalcharacteristics (including changes to the radiation intensitydistribution and/or the phase distribution caused by a given designlayout) of a design layout, which is the representation of anarrangement of features on or formed by the patterning device. Thedesign layout model 1320 can represent one or more physical propertiesof a physical patterning device, as described, for example, in U.S. Pat.No. 7,587,704, which is incorporated by reference in its entirety. Sincethe patterning device used in the lithographic projection apparatus canbe changed, it is desirable to separate the optical properties of thepatterning device from the optical properties of the rest of thelithographic projection apparatus including at least the illuminationand the projection optics.

An aerial image 1330 can be simulated from the source model 1300, theprojection optics model 1310 and the design layout model 1320. An aerialimage (AI) is the radiation intensity distribution at substrate level.Optical properties of the lithographic projection apparatus (e.g.,properties of the illumination, the patterning device and the projectionoptics) dictate the aerial image.

A resist layer on a substrate is exposed by the aerial image and theaerial image is transferred to the resist layer as a latent “resistimage” (RI) therein. The resist image (RI) can be defined as a spatialdistribution of solubility of the resist in the resist layer. A resistimage 1350 can be simulated from the aerial image 1330 using a resistmodel 1340. The resist model can be used to calculate the resist imagefrom the aerial image, an example of which can be found in U.S. PatentApplication Publication No. US 2009-0157360, the disclosure of which ishereby incorporated by reference in its entirety. The resist model istypically related only to properties of the resist layer (e.g., effectsof chemical processes which occur during exposure, post-exposure bakeand development).

Simulation of the lithography can, for example, predict contours and/orCDs in the resist image. Thus, the objective of the simulation is toaccurately predict, for example, edge placement, and/or aerial imageintensity slope, and/or CD, etc. of the printed pattern. These valuescan be compared against an intended design to, e.g., correct thepatterning process, identify where a defect is predicted to occur, etc.The intended design is generally defined as a pre-OPC design layoutwhich can be provided in a standardized digital file format such asGDSII or OASIS or other file format.

From the design layout, one or more portions may be identified, whichare referred to as “clips”. In an embodiment, a set of clips isextracted, which represents the complicated patterns in the designlayout (e.g., about 500 to 800,000 clips, although any number of clipsmay be used). These patterns or clips represent small portions (i.e.circuits, cells or patterns) of the design and more specifically, theclips typically represent small portions for which particular attentionand/or verification is needed. In other words, clips may be the portionsof the design layout, or may be similar or have a similar behavior ofportions of the design layout, where one or more critical features areidentified either by experience (including clips provided by acustomer), by trial and error, or by running a full-chip simulation.Clips may contain one or more test patterns or gauge patterns. Thoseclips that are predicted having a defect when printed are referred to ashotspots.

An initial larger set of clips may be provided, e.g., a priori by acustomer based on one or more known critical feature areas in a designlayout which require particular attention. Alternatively, in anotherembodiment, an initial larger set of clips may be extracted from theentire design layout by using some kind of automated (such as machinevision) or manual algorithm that identifies the one or more criticalfeature areas.

Further, in order that the substrate that is processed (e.g., exposed)by the lithographic apparatus is processed correctly and consistently,it is desirable to inspect a processed substrate to measure one or moreproperties such as overlay error between subsequent layers, linethickness, critical dimension (CD), etc. If an error is detected, anadjustment may be made to processing of one or more subsequentsubstrates. This may particularly useful, for example, if the inspectioncan be done soon and fast enough that another substrate of the samebatch is still to be processed. Also, an already processed substrate maybe stripped and reworked (to improve yield) or discarded, therebyavoiding performing a pattern transfer on a substrate that is known tobe faulty. In a case where only some target portions of a substrate arefaulty, a further pattern transfer may be performed only on those targetportions which are good. Another possibility is to adapt a setting of asubsequent process step to compensate for the error, e.g. the time of atrim etch step can be adjusted to compensate for substrate-to-substrateCD variation resulting from a lithographic process step.

In a similar manner, a patterning device (e.g., a reticle) can beinspected to determine whether there are any errors in the pattern onthe patterning device. Such inspection can determine a registrationerror (e.g., a difference in placement between a portion of a pattern as“written” on a patterning device as compared to the designed placement)and/or dimension (e.g., feature width, feature length, etc.) of afeature of the pattern on the patterning device.

An inspection apparatus is used to determine one or more properties of asubstrate, and in particular, how one or more properties of differentsubstrates or different layers of the same substrate vary from layer tolayer and/or across a substrate and/or across different substrates,e.g., from substrate to substrate. The inspection apparatus may beintegrated into the lithographic apparatus LA or the lithocell LC or maybe a stand-alone device. To enable most rapid measurements, it isdesirable that the inspection apparatus measure one or more propertiesin the patterned resist layer immediately after pattern transfer.However, the latent pattern in the resist may have a very lowcontrast—e.g., there is only a very small difference in refractive indexbetween the part of the resist which has been exposed to radiation andthat which has not—and not all inspection apparatuses have sufficientsensitivity to make useful measurements of the latent pattern. Thereforemeasurements may be taken after a post-exposure bake step (PEB) which iscustomarily the first step carried out on a patterned substrate andincreases the contrast between, e.g., exposed and unexposed parts of theresist. At this stage, the pattern in the resist may be referred to assemi-latent. It is also possible to make measurements of the developedresist image—at which point, e.g., either the exposed or unexposed partsof the resist have been removed—or after a pattern transfer step such asetching. The latter possibility limits the possibility for rework of afaulty substrate but may still provide useful information, e.g. for thepurpose of process control.

Inspection apparatus to determine one or more properties of an object(such as a semiconductor substrate, patterning device, etc.) can takevarious different forms. For example, the inspection apparatus may usephoton electromagnetic radiation to illuminate the object and detectradiation redirected by the object; such inspection apparatuses may bereferred to as bright-field inspection apparatuses. A bright-fieldinspection apparatus may use radiation with a wavelength in, forexample, the range of 150-900 nm. The inspection apparatus may beimage-based, i.e., taking an image of the object, and/ordiffraction-based, i.e., measuring intensity of diffracted radiation.The inspection apparatus may inspect product features (e.g., features ofan integrated circuit to be formed using a substrate or features of amask) and/or inspect specific measurement targets (e.g., overlaytargets, focus/dose targets, CD gauge patterns, etc.).

Inspection of, e.g., semiconductor wafers is done mostly withoptics-based sub-resolution tools (bright-field inspection). But, insome cases, certain features to be measured are too small to beeffectively measured using bright-field inspection. For example,bright-field inspection of defects in features of a semiconductor devicecan be challenging. Moreover, as time progresses, features that arebeing made using patterning processes (e.g., semiconductor features madeusing lithography) are becoming smaller and in many cases, the densityof features is also increasing. So, future semiconductor nodes challengethe scalability of current optical inspection for measuring smalldefects (e.g., pattern shape defects, electrical defects, etc.) and tomeasure the smaller and/or denser features of those nodes, due to theresolution limits of bright-field inspection. Further, bright-fieldinspection can have relatively lower capture rate and/or, for a givencapture rate, an increasing nuisance rate, which can lead to increasedtime and costs spent using bright-field inspection.

Accordingly, a higher resolution inspection technique is used anddesired. An example inspection technique is electron beam inspection.Electron beam inspection involves focusing a beam of electrons on asmall spot on the object to be inspected. An image is formed byproviding relative movement between the beam and the object (hereinafterreferred to as scanning the electron beam) over the area of the objectinspected and collecting secondary and/or backscattered electrons withan electron detector. The image data is then processed to, for example,identify defects.

So, in an embodiment, the inspection apparatus may be an electron beaminspection apparatus (e.g., the same as or similar to a scanningelectron microscope (SEM)) that yields an image of a structure (e.g.,some or all the structure of a device, such as an integrated circuit) onthe object. FIG. 3 depicts an embodiment of an electron beam inspectionapparatus 200. A primary electron beam 202 emitted from an electronsource 201 is converged by condenser lens 203 and then passes through abeam deflector 204, an E×B deflector 205, and an objective lens 206 toirradiate an object 100 on a table 101 at a focus.

When the object 100 is irradiated with electron beam 202, secondaryelectrons are generated from the object 100. The secondary electrons aredeflected, e.g. by an E×B deflector 205 and detected by a secondaryelectron detector 207. A two-dimensional electron beam image can beobtained by detecting the electrons generated from the sample insynchronization with, e.g., two dimensional scanning of the electronbeam by beam deflector 204 or with repetitive scanning of electron beam202 by beam deflector 204 in an X or Y direction, together withcontinuous movement of the object 100 by the table 101 in the other ofthe X or Y direction. Thus, in an embodiment, the electron beaminspection apparatus has a field of view for the electron beam definedby the angular range into which the electron beam can be provided by theelectron beam inspection apparatus (e.g., the angular range throughwhich the deflector 204 can provide the electron beam 202). Thus, thespatial extent of the field of the view is the spatial extent to whichthe angular range of the electron beam can impinge on a surface (whereinthe surface can be stationary or can move with respect to the field).

A signal detected by secondary electron detector 207 is converted to adigital signal by an analog/digital (A/D) converter 208, and the digitalsignal is sent to an image processing system 300. In an embodiment, theimage processing system 300 may have memory 303 to store all or part ofdigital images for processing by a processing unit 304. The processingunit 304 (e.g., specially designed hardware or a combination of hardwareand software) is configured to convert or process the digital imagesinto datasets representative of the digital images. Further, imageprocessing system 300 may have a storage medium 301 configured to storethe digital images and corresponding datasets in a reference database. Adisplay device 302 may be connected with the image processing system300, so that an operator can conduct necessary operation of theequipment with the help of a graphical user interface.

The apparatus depicted in FIG. 3 is an example of a single electron beamcolumn inspection system; it has a single electron beam column thatproduces, controls and detects a single electron beam. But, a singleelectron beam column inspection system can take a long time to inspectan object, such as a standard 300 mm wafer. This can be furtherexacerbated by the desire to measure smaller defects and/or features,which require a smaller beam size. Using smaller beam or pixel sizes todetect smaller defects and/or features may lead to noise and loss inthroughput (e.g., due to reducing the electron current to limit anydamage to the object). Increased electron current can increasethroughput but has repercussions on resolution.

Thus, a single electron beam column inspection system can besignificantly constrained in terms of throughput (e.g., inspection areaper unit time) and is currently too slow for high-volume manufacturing.For example, there could be a throughput gap between a single electronbeam column inspection system and bright-field inspection of about ˜3-4orders of magnitude. Thus, there is a desire to provide high resolutioninspection with high throughput. In an embodiment, there is providedelectron beam-based inspection with throughput comparable tobright-field based inspection.

In an embodiment, throughput can be increased by providing a pluralityof electron beams from a particular electron beam column (hereinafterreferred to as multi-beam column). Thus, the field of view of theelectron beam inspection apparatus can be extended by adding multiplebeams side by side in an array/matrix to create an effective field ofview that is a multiple of the individual fields of view of individualbeams. For example, beams can be provided with a pitch of 10 micronsforming, e.g., a 10×10 matrix of beams (each with a 10×10 microns fieldof view at the object) with a combined field of view of 100×100 microns.This array of beams can then scan an object 100 times faster than asingle beam with a field of view of 10×10 microns. But, even such a gainmay not be enough.

Referring to FIG. 4, an example of an implementation of the multiplebeams of a multi-beam column electron beam inspection system in thecontext of an object 100 (e.g., a semiconductor wafer, a reticle, etc.).In this case, the object 100 comprises a plurality of fields or dies 120identified by their respective boundaries 125 (which boundaries may notbe physically present on the object but rather be “imaginary”boundaries). In an embodiment, a die corresponds to a portion of anobject that becomes an individual device. That is, where the object is asemiconductor wafer, the object is cut into pieces corresponding to thedies, each die becoming, e.g., a semiconductor device. In an embodiment,a field corresponds to the size of the exposure field of a lithographicapparatus used to pattern a substrate. A field may comprise plurality ofdies, where, e.g., the patterning device provides a pattern comprising aplurality of dies. The object in FIG. 4 is highly schematic and willtypically have many more dies/fields than shown. While a round object isdepicted, it could be a different shape. The width (e.g., diameter) ofthe object can vary. For example, the width may be 300 nm or 450 nm. Inan embodiment, an object will have about 30 or more die/fields, about 40or more die/fields, about 50 or more die/fields, about 60 or moredie/fields, about 70 or more die/fields, about 80 or more die/fields,about 90 or more die/fields, about 100 or more die/fields, about 110 ormore die/fields, about 120 or more die/fields, about 130 or moredie/fields, about 140 or more die/fields, about 150 or more die/fields,about 160 or more die/fields, about 170 or more die/fields, about 180 ormore die/fields, about 190 or more die/fields, about 200 or moredie/fields, about 220 or more die/fields, about 240 or more die/fields,or about 260 or more die/fields.

As shown in FIG. 4, the multiple beams present a combined field of view400 in which the beams inspect the object 100. In this example, thereare four beams, each with its own field of view of the combined field ofview and which respective fields of view need not be equal. In thiscase, each beam has an equal field of view, as represented by the foursegments in FIG. 4, of the combined field of view 400. Thus, in anembodiment, there is provided relative movement between the combinedfield of view 400 and the object 100, in order that the beams caninspect different portions (e.g., fields/dies 120 or portions thereof)of the object, including defects 410. In an embodiment, if each of thebeams has a width corresponding to its respective field of view of thecombined field of view 400, then the beams could be in a generally fixedorientation and the object is moved relative to the beams to inspect theobject. Further, in an embodiment, there is a relative movement betweenan electron beam and the object to provide scanning of the beam with itsrespective field of view within the combined field of view 400. In anembodiment, the object is in a generally fixed orientation and the beamsare moved (e.g., tilted) relative to the object to cause scanning of thebeams within their respective fields of view. In an embodiment, theremay be a combined movement of the beams and the object to cause scanningof the beams with their respective fields of view. So, in an embodiment,by relative movement between the combined field of view 400 and theobject, the plurality of beams can be provided to different parts of theobject, such as the plurality of fields/dies 120 or portions thereof,and once at a part of the object, relative movement is provided betweenthe electron beams and the object to provide scanning of the beams withtheir respective fields of the combined field of view 400, to image theobject, including the defects 410.

The combined field of view 400, and the individual field of viewportions thereof corresponding to the respective beams, can havedifferent shapes than as shown in FIG. 4. As noted above, in anembodiment, the boundary of each beam spot is co-extensive with itsportion of the field of view 400. In an embodiment, the beam spot issmaller than the beam's portion of the field of view and thuseffectively relative motion is provided between the beam and its portionof field of view 400 so that the beam can inspect the regioncorresponding to its portion of the field of view. In such anembodiment, the beams may be caused to move (e.g., tilt) in order toprovide the relative movement between the beam and its portion of thefield of view 400 and the object may be caused to move to provide therelative movement between the field of view 400 and the object. Adifferent combination of movements may be provided as appropriate.

In an embodiment, throughput and/or the ability to measure smallerfeatures can be improved by providing a plurality of electron beamcolumns, each of which provides at least a single electron beam(hereinafter referred to as a multi-column system). That is, each columnprovides at least a single electron beam (in an embodiment, one or moreof the plurality electron beam columns is a multi-beam column) and has adetector to measure secondary and/or backscattered electrons arisingfrom the column's electron beam being incident on the object. In anembodiment, each of the electron beam columns, or a plurality ofelectron beams selected from the electron beam columns, inspects theobject in parallel with one or more other electron beam columns. So, inan embodiment, each beam may have a relatively small current for betterresolution, but in total, the multiple electron beam columns provide arelatively high total current to enable faster inspection. Further,acquisition of images in parallel through the use of a plurality ofelectron beam columns enables a significant increase in throughputcompared to a single electron beam column.

Referring to FIG. 5, a highly schematic example is shown of animplementation of the multiple beams of an embodiment of a multi-columnelectron beam inspection system in the context of an object 100. In thiscase, the object 100 comprises a plurality of fields or dies 120identified by their respective boundaries 125 (which boundaries may notbe physically present on the object but rather be “imaginary”boundaries). In an embodiment, each of the fields or dies has anelectron beam column allocated to it. In an embodiment, each set of aplurality of sets, each set comprising a plurality of fields or dies,has an electron beam column allocated to it. In an embodiment, theplurality of electron beam columns is provided in a one dimensionalarray, desirably a one-dimensional array with enough electron beamcolumns to extend across the widest portion of the object. In anembodiment, the one dimensional array effectively scans across theobject through relative movement between the array and the object in adirection orthogonal to the direction of elongation of the array. In anembodiment, the electron beam columns are arranged in a two-dimensionalarray. In an embodiment, the two-dimensional array extends across thewidth/length of the object in a first direction and across thewidth/length of the object in a second direction orthogonal to the firstdirection. In an embodiment, the two-dimensional array is a rectangulararray. In an embodiment, two-dimensional array has a shape matching theshape of the object. So, for a round object, the array may be arectangular array with array elements at the corners removed to make agenerally circular array or may be diamond-shaped.

In an embodiment, an object will have about 30 or more electron beamcolumns allocated to the object, about 40 or more electron beam columnsallocated to the object, about 50 or more electron beam columnsallocated to the object, about 60 or more electron beam columnsallocated to the object, about 70 or more electron beam columnsallocated to the object, about 80 or more electron beam columnsallocated to the object, about 90 or more electron beam columnsallocated to the object, about 100 or more electron beam columnsallocated to the object, about 110 or more electron beam columnsallocated to the object, about 120 or more electron beam columnsallocated to the object, about 130 or more electron beam columnsallocated to the object, about 140 or more electron beam columnsallocated to the object, about 150 or more electron beam columnsallocated to the object, about 160 or more electron beam columnsallocated to the object, about 170 or more electron beam columnsallocated to the object, about 180 or more electron beam columnsallocated to the object, about 190 or more electron beam columnsallocated to the object, about 200 or more electron beam columnsallocated to the object, about 220 or more electron beam columnsallocated to the object, about 240 or more electron beam columnsallocated to the object, or about 260 or more electron beam columnsallocated to the object. The object in FIG. 5 is highly schematic andwill typically have many more dies/fields than shown. While a roundobject is depicted, it could be a different shape. The width (e.g.,diameter) of the object can vary.

As shown in FIG. 5, each beam of the plurality of beams has a respectivefield of view 500 in which the beam inspects the object 100. In thisexample, there are five beams, each with its own field of view 500.Thus, in an embodiment, there is provided relative movement between thebeams and the object, which effectively causes relative movement betweenthe fields of view 500 and the object 100, in order that the beamsinspect different parts of the object, including defects 410. In anembodiment, each of the fields of view 500 is effectively dedicated to arespective field or die. That is, in an embodiment, the majority of adie or field is inspected with only a single field of view 500 of theplurality of fields of view 500. In an embodiment, each field of view500 for a die or field inspects less than a majority, including none, ofan adjacent die or field. In an embodiment, a field of view 500 does notinspect a die or field other than the one to which the field of view 500is associated.

Thus, in an embodiment, there is provided relative movement between thefields of view 500 and the object 100 such that each field of view 500inspects different portions of its associated die or field. In anembodiment, the fields of view 500 are in generally fixed orientationand the object is moved relative to the fields of view 500 to place thefields of view 500 at their respective portions of their respectivefields or dies.

Once each of the fields of view 500 is located at its respective part ofits respective die or field, each of the respective beams then inspectsits respective part of its die or field in parallel with the otherbeams. In an embodiment, where a field of view 500 corresponds to thesize of the electron beam spot, the beam is in a generally fixedorientation and the object is moved relative to the beam to causescanning of the beam in the respective field or die. More typically, inan embodiment, the object is in a generally fixed orientation and therespective beams are moved (e.g., tilted) relative to the object tocause scanning of the beams within their respective fields of view inthe respective field or die. In an embodiment, there may be a combinedmovement of the beams and the object to cause scanning of the beams.

So, in an embodiment, through relative movement between the fields ofview 500 and the object 100, each of the beams (which operate in thefield of view 500) are respectively stepped to different parts of itsrespective field/die 120 to image those different parts (typicallythrough scanning of the respective beams by movement of the beam and/orof the object), including actual or suspected defects 410. Moreover, toenable throughput improvement, the parts of the different fields/dies120 are inspected in parallel by the beams in their respective fields ofview 500, i.e., a plurality of beams are projected at the object at asame to such that each beam inspects its respective field or die.

In an embodiment, the fields of view 500 that correspond to respectivebeams can have different shapes than as shown in FIG. 4. In anembodiment, the boundary of each beam spot is co-extensive with itsfield of view 500. In an embodiment, the beam spot is smaller than thebeam's field of view and thus effectively relative motion is providedbetween the beam and its field of view 500 so that the beam can inspectthe region corresponding to the field of view 500. In such anembodiment, the beams may be caused to move (e.g., tilt) in order toprovide the relative movement between the beam and its field of view andthe object may be caused to move to provide the relative movementbetween the fields of view 500 and the object. A different combinationof movements may be provided as appropriate.

FIG. 6 is a highly schematic representation of an embodiment of amulti-column electron beam inspection system comprising an array ofelectron beam columns 600, each electron beam column corresponding to atleast one die or field on object 100. Thus, in an embodiment, aplurality of miniature electron beam columns is arranged in an array(e.g., a substantially horizontal array)—in this case, a two-dimensionalarray. For example, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140,150, or 160 or more optical columns may be provided in a two-dimensionalarray. In an embodiment, the number of optical columns corresponds to atleast the number of fields or dies on the object 100. The array ofelectron beam columns enables cross-object inspection in parallel, i.e.,at least one of the electron beam columns inspects a portion of theobject at a same time as another at least one of the electron beamcolumns inspects another portion of the object.

Each electron beam column is miniature (e.g. 200 mm² or less, 170 mm² orless, 150 mm² or less, 120 mm² or less, 100 mm² or less, 80 mm² or less,60 mm² or less, such as 10×10 mm or smaller in either or bothdimensions). Further, each electron beam column provides at least oneelectron beam and has at least one detector. In an embodiment, eachelectron beam column is effectively an independent electron beam system.As noted above, in an embodiment, each column is placed in a patternmatching the position of each field or die on the object 100. With a 100dies or fields of an object (e.g., a 300 mm diameter semiconductorsubstrate), there would be provided, e.g., 100 separate electron beamcolumns, each spaced by 1-30 millimeters from another (as distinct fromthe few micrometers space between multiple beams in a single columnmulti-beam inspection system).

In an embodiment, one or more of the electron beam columns are movablerelative to another one or more of the electron beam columns. In anembodiment, each of the electron beam columns is independently movable.In an embodiment, an electron beam column is movable in a firstdirection and in a second direction essentially orthogonal to the firstdirection. In an embodiment, one or more groups of electron beamcolumns, each group comprising a plurality of electron beam columns, aremovable relative to one or more other electron beam columns. Forexample, a column or row of electron beam columns is movable relativeanother respective column or row of electron beam columns.

Referring to FIG. 6, an embodiment of actuator system is presented formoving electron beam columns. In this embodiment, a plurality ofelectron beam columns is mounted on a structure 610, a further pluralityof electron beam columns is mounted on a further structure 610, and soon as appropriate. An actuator 620 of the actuator system causes atleast one of the structures 610 to move in a first direction 640 tochange a position of the at least one structure 610 relative to anotherstructure 610. In an embodiment, the actuator 620 is arranged to changethe pitch of the structures 610 (and thus the electron beam columns 600)in the direction 640 and thus change the spacing of the structures 610uniformly. In an embodiment, the change in pitch is such that the pitchchanges from a first uniform pitch among the structures 610 to a seconddifferent uniform pitch among the structures 610. In an embodiment, theactuator 620 is configured to move each of the structures 610independently such that almost any spacing arrangement between thestructures 610 can be provided. In an embodiment, the actuator 620comprises a linear motor, a piezoelectric actuator and/or a belt system.In an embodiment, the actuator 620 can move the structure 610 in up toand including 6 degrees of freedom.

In an embodiment, the actuator system is configured to move the electronbeam columns in a second direction 630 (which is, in an embodiment,essentially orthogonal to the first direction 640). Details of anembodiment of an actuator to move the electron beam columns 600 in thedirection 630 will be described in respect of FIGS. 8 and 9.

FIG. 7 is a highly schematic perspective view of an embodiment of amulti-column electron beam apparatus of the type described in respect ofFIG. 6. As can be seen in FIG. 7, the electron beam columns 600 extendacross the width/length of the object 100. While the electron beamcolumns 600 are shown as extending from the structures 610 in FIGS. 7and 8, the electron beam columns 600 may be integrated inside of thestructures 610 (e.g., the structure 610 is generally U-shaped toaccommodate the electron beam columns in the U-shape).

FIG. 8 is a highly schematic side view of an embodiment of electron beamcolumn 600. The electron beam column includes electron beam optics 800,electron beam processing equipment 810, an optional sensor 820, anactuator portion 840, and an optional actuator 860. FIG. 9 is a highlyschematic top or bottom view of the embodiment of the electron beamcolumn 600 of FIG. 8.

In an embodiment, the electron beam optics 800 comprises an electronbeam source to produce the electron beam 805. In an embodiment, theelectron beam optics 800 comprises one or more optical elements to focusand direct the electron beam toward the object (not shown here forconvenience).

The electron beam processing equipment 810 comprises a detectorconfigured to sense secondary and/or backscattered electrons from theobject, the secondary and/or backscattered electrons arising from thebeam from the electron beam optics 800 being incident on the object.Thus, the electron beam column acts as integrated supplier and detectorof an electron beam to inspect a particular area of the object.

In an embodiment, the electron beam processing equipment 810 optionallycomprises optics/structure that is configured to cause movement of thebeam, e.g., tilt the beam. Thus, in this case, the electron beam columnhas a field of view wider than the width of the beam itself. Suchoptics/structure may move the beam (e.g., with a 1-30 nm spot size)within the field of view of the electron beam column, e.g., scan thefield of view of the electron beam column. In an embodiment, theoptics/structure are electrostatic. In an embodiment, theoptics/structure, if any, of the electron beam processing equipment 810and the electron beam optics 800 may all be electrostatic, i.e., thereare no magnetic elements for processing the electron beam after emissionand before incidence on the object. Such an arrangement enables a smallelectron beam column with optionally fast deflection. Alternatively, inanother embodiment permanent magnetic elements combined withelectrostatic elements may enable an alternative embodiment of a smallcolumn.

In an embodiment, the electron beam processing equipment 810 optionallycomprises an electron column control system. The electron column controlsystem enables control of the electron optics 800, the optionaloptics/structure configured to cause movement of the beam, the detector,the actuator portion 840 and/or 850, and/or the optional actuator 860.In an embodiment, the electron column control system comprises a centralprocessing unit and local data storage to enable individual control bythe electron beam column and thus effectively independent electron beaminspection. In an embodiment, each electron beam column has anidentical, or nearly identical, datapath. So, as the electron beams arescanned over the object, images from each electron beam column arecollected by its detector and the image data is transferred to theelectron column's control system. The detection and processing at eachcolumn in parallel helps to avoid bottlenecks and enable high datavolumes and rates.

In an embodiment, actuator portion 840 (of the actuator system, whichincludes actuator 620) enables the electron beam column 600 to move inthe second direction 630 to change a position of the electron beamcolumn 600 relative to another electron beam column. In an embodiment,the actuator portion 840 cooperates with actuator portion 850 located inor on the structure 610 to which the electron beam column 600 isattached. In an embodiment, the actuator portion 840 may comprise a coilor magnet and the actuator portion 850 may be the cooperating magnet orcoil. In an embodiment, actuator portions 840, 850 form a linear motor.In an embodiment, only actuator portion 840 may be provided, e.g., apiezoelectric actuator. In an embodiment, only actuator portion 850 inor on the structure 610 is provided, e.g., a mechanical motor or beltsystem, to move the electron beam column 600. In an embodiment, theactuator portion 850 extends along a plurality of the electron beamcolumns (e.g., the length of the structure 610) or comprises portionsalong structure 610 corresponding to each electron beam column 600. Inan embodiment, the actuator portion 840 and/or 850 is arranged to changethe pitch of the electron beam columns 600 on a structure 610 in thedirection 630 and thus change the spacing of the electron beam columns600 uniformly. In an embodiment, the change in pitch is such that thepitch changes from a first uniform pitch among the electron beam columns600 to a second different uniform pitch among the electron beam columns600. In an embodiment, the actuator portion 840 and/or 850 is configuredto move each of electron beam columns 600 independently such that almostany spacing arrangement between electron beam columns 600 along astructure 610 can be provided. In an embodiment, the actuator portion840 and/or 850 comprises a linear motor, a piezoelectric actuator and/ora belt system. In an embodiment, the actuator portion 840 and/or 850 canmove the electron beam column in up to and including 6 degrees offreedom.

FIG. 14 is a highly schematic representation of an embodiment of amulti-column electron beam inspection system comprising an array ofelectron beam columns 600, each electron beam column corresponding to atleast one die or field on object 100. Thus, in an embodiment, aplurality of miniature electron beam columns is arranged in an array(e.g., a substantially horizontal array)—in this case, a two-dimensionalarray. The array of electron beam columns enables cross-objectinspection in parallel, i.e., at least one of the electron beam columnsinspects a portion of the object at a same time as another at least oneof the electron beam columns inspects another portion of the object.

In an embodiment, one or more of the electron beam columns are movablerelative to another one or more of the electron beam columns. In anembodiment, an electron beam column is movable in a first direction andin a second direction essentially orthogonal to the first direction. Inan embodiment, one or more groups of electron beam columns, each groupcomprising a plurality of electron beam columns, are movable relative toone or more other electron beam columns. For example, a column or row ofelectron beam columns is movable relative another respective column orrow of electron beam columns.

In this embodiment, a combination of long and short stroke positioningunits are provided to position each electron beam column within the scanfield on the object. For the long stroke movement, a grid of structuresare provided to independently move clusters of electron beam columns intwo generally orthogonal directions (e.g., X or in Y), as shownschematically in the top or bottom view of FIG. 14. The short strokepositioning unit will be described hereafter in respect of FIG. 15 andincludes a two-dimensional short stroke actuator for an individualelectron beam column. A typical number of scan fields on an object is100, so a grid of for example 10×10 electron beam columns involves 10structures along the X-direction and 10 structures along theY-direction. The schematic example of FIG. 14 shows 4 columns along theX-direction and 3 rows along the Y-direction. In an embodiment, the gridcomprises a plurality of structures essentially perpendicular withanother plurality of the structures, but in an embodiment, thestructures need not be perpendicular.

Referring to FIG. 14, an embodiment of a long stroke actuator system ispresented for moving electron beam columns. In this embodiment, aplurality of electron beam columns is mounted on a structure 1300, afurther plurality of electron beam columns is mounted on a furtherstructure 1300, and so on as appropriate. An actuator 1310 of theactuator system causes at least one of the structures 1300 to move in afirst direction 1320 to change a position of the at least one structure1300 relative to another structure 1300. In an embodiment, the actuator1310 is arranged to change the pitch of the structures 1300 (and thusthe electron beam columns 600) in the direction 1320 and thus change thespacing of the structures 1300 uniformly. In an embodiment, the changein pitch is such that the pitch changes from a first uniform pitch amongthe structures 1300 to a second different uniform pitch among thestructures 1300. In an embodiment, the actuator 1310 is configured tomove each of the structures 1300 independently such that almost anyspacing arrangement between the structures 1300 can be provided. In anembodiment, the actuator 1310 can move each or a combination ofstructures 1300 in up to and including 6 degrees of freedom.

In this embodiment, a plurality of electron beam columns is mounted on astructure 1330, a further plurality of electron beam columns is mountedon a further structure 1330, and so on as appropriate. In an embodiment,the electron beam columns mounted to structures 1330 are those mountedto structures 1300. An actuator 1340 of the actuator system causes atleast one of the structures 1330 to move in a second direction 1350(which is, in an embodiment, essentially orthogonal to the firstdirection 1320) to change a position of the at least one structure 1330relative to another structure 1330. In an embodiment, the actuator 1340is arranged to change the pitch of the structures 1330 (and thus theelectron beam columns 600) in the direction 1350 and thus change thespacing of the structures 1330 uniformly. In an embodiment, the changein pitch is such that the pitch changes from a first uniform pitch amongthe structures 1330 to a second different uniform pitch among thestructures 1330. In an embodiment, the actuator 1340 is configured tomove each of the structures 1330 independently such that almost anyspacing arrangement between the structures 1330 can be provided. In anembodiment, the actuator 1340 can move each or a combination ofstructures 1330 in up to and including 6 degrees of freedom.

In FIG. 14 (and shown in FIG. 15), the structures 1330 overlap thestructures 1300. While structures 1330 are shown overlying structures1300, they need not be. For example, structures 1300 could be overlyingstructures 1330. As another example, the structures 1300 and 1330 couldbe effectively interwoven such that portions of a structure 1300 arebetween adjacent structures 1330 (or vice versa). As another example,the structures 1300 could pass through the body of structures 1330 (orvice versa) using one or more appropriate slots.

In an embodiment, the actuator 1310 and/or actuator 1340 comprises alinear motor, a piezoelectric actuator and/or a belt system. In anembodiment, the actuator 1310 can move a structure 1300 in up to andincluding 6 degrees of freedom and/or the actuator 1340 can move astructure 1330 in up to and including 6 degrees of freedom. In anembodiment, the actuator 1310 and/or actuator 1340 can provide, forexample, up to 200 mm range (e.g., up 50 mm range, up to 100 mm range,up to 150 mm range) at up to 200 mm/s (e.g., up to 50 mm/s, up to 100mm/s, up to 150 mm/s) for long stroke movement. In an embodiment, theactuator 1310 and/or actuator 1340 provide a lateral accuracy in therange of 10-100 μm.

In an embodiment, the one or more of motors for the long stroke movementand/or for the short stroke movement are not significantly influenced byelectric and/or magnetic fields (and desirably should not provideelectric and/or magnetic fields that influence an electron beam column600). In an embodiment, the motors for the long stroke movement and/orfor the short stroke movement are piezo-electric motors. Apiezo-electric motor is typically insensitive to electric and/ormagnetic fields. In an embodiment, the piezo-electric motor providesessentially no electric and/or magnetic fields. A piezo motor (e.g.,linear, walk, hexapod, etc. piezo-motor) can provide the range and/orspeed for respective the long stroke movement and/or for the shortstroke movement.

Referring to FIG. 15, in an embodiment, independent long stroke movementin the first and second directions 1320, 1350 is achieved by applying,for example, a gear box type construction. FIG. 15 is highly schematicside view of an embodiment of a double structure gear box type mechanismfor long stroke movement of electron beam columns 600 in parallel, wherethe electron beam columns 600 can be placed, for example, below the longstroke positioning unit using structures 1300, 1330. A structure 1400(e.g., a rod or pole) is provided onto which is attached a short strokeactuator 1410. Onto the short stroke actuator 1410 is attached anelectron beam column 600.

In an embodiment, the short stroke actuator 1410 enables fine movementof the electron beam column 600 in, e.g., up to 6 degrees of freedom,including, e.g., the first and second directions 1320, 1350. In anembodiment, the actuator 1410 comprises a linear motor, a piezoelectricactuator and/or a belt system. In an embodiment, the actuator 1410comprises a piezo electric motor. In an embodiment, the actuator 1410can provide, for example, up to 20 mm range (e.g., up 5 mm range, up to10 mm range, up to 15 mm range) for fine stroke movement. As will beappreciated, the range of the actuator 1410 would typically be smallerthan the range of the actuators 1310, 1340. In an embodiment, actuator1410 has dimensions within the size of a single scan field on the objectto prevent the electron beam columns 600 from hindering each other.

The structure 1400 can move along a structure 1330 in the firstdirection 1320 (which structure 1330 can be moved in the seconddirection 1350 by actuator 1340) and along a structure 1300 in thesecond direction 1350 (which structure 1300 can be moved in the firstdirection 1320 by the actuator 1310 (not shown in FIG. 15)). In anembodiment, the structure 1400 (with the attached electron beam column600) is guided for movement along the structure 1330 by a bearing 1420attached to the structure 1400. In an embodiment, the bearing 1420 isguided by an interior (as shown in FIG. 15) or exterior surface of thestructure 1330. In an embodiment, the structure 1400 (with the attachedelectron beam column 600) is guided for movement along the structure1300 by a bearing 1430 attached to the structure 1400. In an embodiment,the bearing 1430 is guided by an interior (as shown in FIG. 15) orexterior surface of the structure 1300. In an embodiment, actuator 1410allows for short stroke positioning within 2 μm lateral accuracy withineach specific scan field.

Further, separate brakes 1440, 1450 are provided to allow the separatemovement of the structure 1400 and the attached electron beam column 600in the first and second directions 1320, 1350. In an embodiment, thebrakes are actuated to be closed or open by respectively actuators 1460,1470. If the brake 1440 is closed against the structure 1330, thestructure 1400 and the attached electron beam column 600 are fixed inposition on the structure 1330 (and thus the structure 1400 and theattached electron beam column 600 cannot move relative to the structure1330 while the brake 1440 is closed and so, in an embodiment, cannotmove in a long stroke manner in the first direction 1320 while the brake1440 is closed). In FIG. 15, however, the brake 1440 is shown as openand so the structure 1400 and the attached electron beam column 600 canmove along structure 1330 when structure 1300 is moved in the firstdirection 1320. To enable movement of the structure 1400 and theattached electron beam column 600 with the structure 1300 in the firstdirection 1320, the brake 1450 is closed as shown in FIG. 15 such thatthe structure 1400 and the attached electron beam column 600 are fixedin position on the structure 1300. In order for the structure 1400 andthe attached electron beam column 600 to move in the second direction1350 along structure 1300, the brake 1450 would be opened and the brake1440 closed and then the structure 1330 would be moved in the seconddirection 1350 by actuator 1340. Thus, by selective opening and closingof brakes 1440, 1450 by actuators 1460, 1470 in combination withmovement of the structures 1300, 1330, the structure 1400 and theattached electron beam column 600 can be moved to a desired position. Aswill be appreciated, a plurality of structures 1400 with respectiveattached electron beam columns 600 can be provided, each having arespective set of brakes 1440, 1450. In an embodiment, a single actuatorcan be provided for both brakes 1440, 1450. In an embodiment, the brakes1440, 1450 are operated manually.

Referring to FIG. 16A, one or more of the electron beam columns 600 canbe placed below (or above) the long stroke system comprising a grid ofoverlapping structures 1300, 1330, as shown in FIGS. 2 and 3. Thus, inan embodiment, all of an electron beam column 600 is located below thelowest (or above the highest) structure 1300, 1330. In the example ofFIGS. 2 and 16A, each of the electron beam columns 600 is located atpartly underneath (or above) the center of an intersection of astructure 1300 with a structure 1330. As will be appreciated, theintersection is an imaginary location where overlapping structurescross. FIG. 17A shows an example of an electron beam column 600 locatedcompletely below the lowest (or above the highest) structure 1300, 1330and/or located at partly underneath (or above) the center of anintersection of a structure 1300 with a structure 1330.

Referring to FIG. 16B, to save space in the Z direction and/or for addedmechanical stability, one or more of the electron beam columns 600 canbe placed to the side of an adjacent structure 1300 and/or adjacentstructure 1330, e.g., to the side of each intersection, as shown in FIG.16B. Thus, in an embodiment, one or more of the electron beam columns600 is not located underneath (or above) a structure 1300 and/orstructure 1330. FIG. 17B shows an example of an electron beam column 600located to the side of an adjacent structure 1300 and/or adjacentstructure 1330 and/or not located underneath (or above) a structure 1300and/or structure 1330. As shown in FIG. 17B, an electron beam column 600can be located at least partly in a gap between adjacent structures1300/1330 and thus the actuator 1410 and/or electron beam column 600 islocated above a bottom surface (or below a top surface) of the adjacentstructures 1300/1330. In this embodiment, the brake 1440 and/or brake1450 operates against a side of its respective structure 1300, 1330.Thus, in this embodiment, the structure 1400 can be bent to accommodatethe location of the electron beam column 600 in the gap. For example,the structure 1400 can extend from the side of structure 1300 (as seenin FIG. 17B) and/or can extend from the side of the structure 1330 (asseen in FIG. 17B). The embodiment of FIGS. 16B and 17B otherwise use thesame principles of moving the electron beam columns 600 (e.g., usingbrakes 1440, 1450 and movement of structures 1300, 1330).

In an embodiment, one or more of the electron beam columns 600 and/orstructures 1400 can have a metrology module 1480, e.g. a radiationsource (e.g., a laser) and a sensor, to measure the distance to one ormore neighboring electron beam columns 600 and/or structures 1400 inorder to determine its exact position with respect to the object scanfield (e.g., so as to efficiently and/or accurately inspect within itsassociated die or field). Alternatively or additionally, the metrologymodule 1480 can measure the distance between an electron beam column 600and one or more structures 1300, 1330 of the long stroke system in orderto determine its exact position with respect to the object scan field.Additionally or alternatively, the metrology module 1480 (e.g., in theform of sensor 820 as described below) can measure the position of theelectron beam column 600 with respect to the object scan field using oneor more markers on the object, e.g. on each die or field.

In an embodiment, to enable fine positioning, the structures 1300, 1330can be moved in a first, relatively low resolution mode to cause one ormore of the electron beam columns 600 to scan over a relatively largescan area, e.g. more than 1 μm² and up to 200 μm². In an embodiment, oneor more techniques, such as pattern recognition, can be used toaccurately localize a region of interest (e.g. defect area). In a secondstep, a plurality of the electron beam columns 600 are moved to theirinspection positions with high accuracy using, e.g., structures 1300,1330 and/or actuator 1410, and then followed by a high resolution scanover a small area (desirably enclosing the region of interest), such asan area more than 0.1 μm² and up to 2 μm². In an embodiment, for thesecond step, the electron beam columns 600 are not physically moved, butonly the object is moved off-center to perform the small area scanningor both the electron beam columns 600 and the object are moved toperform the small area scanning.

Thus, in an embodiment, there is provided a long stroke systemcomprising overlapping structures holding electron beam columns abovetheir respective scan fields using, e.g., a gear box type ofconstruction to independently move the electron beam columns in twodifferent direction (e.g., in the X and Y directions). In an embodiment,piezo long and short stroke motors can be provided for accuratepositioning and/or electric/magnetic interference free positioning. Inan embodiment, there is provided the possibility to position the shortstroke actuator and/or electron beam column on the side of the longstroke structures.

So, with the actuator system described herein, the electron beam columnscan be arranged to conform to different object sizes. Further, theactuator system can be arranged to conform to different arrangements offields or dies in terms of different size fields or dies, differentpitches of fields or dies, different shapes of fields or dies, etc. Theadjustments are made so that the electron beam columns are each matchedwith a different field or die and so only the general pitch in, e.g., Xand/or Y of the electron beam columns is adjusted so to match theelectron beam columns with a respective field or die location.

Thus, in an embodiment, the plurality of beams are at a pitch that is aninteger times the field or die pitch/spacing. So, in an embodiment, inorder to allow the die or field size or spacing to be variable, theactuator system enables the beams to move over a distance of half thefield or die pitch in X and/or Y. In an embodiment, the electron beamcolumns are spaced at least larger than 2 times the pitch so as toenable the range of movement of the columns.

While an embodiment has described using movable structures 610, themovement of the electron beam columns 600 can be implemented indifferent manner. For example, each of the electron beam columns mayindividually move in the X and Y directions relative to a generallyplanar structure. For example, each electron beam column may have a coilor magnet that cooperates with a planar arrangement of coils andmagnets, akin to a planar motor. Further, while the object is depictedunderneath the electron beam columns in the Figures, the object couldinstead be located above the electron beam columns.

In an embodiment, during inspection, the electron beam columns aresubstantially stationary. Thus, prior to inspection, the electron beamcolumns are adjusted in X and/or Y to match the field or diepositions/sizes, and then the electron beam columns are substantiallyfixed during inspection. During inspection, only the object may be movedrelative to the pre-positioned electron beam columns. Optionally, thebeam may be deflected to enable scanning of the electron beam duringinspection as discussed above.

Further, in an embodiment, referring to FIG. 10, at least the electronbeam optics (which may include up to the entire electron beam column)may be slightly adjusted 1000, 1010 in position (e.g., horizontalposition or tilt) using actuator 860. Such adjustment may occur whilethe object is moved relative to the electron beam columns during theprocessing the object as a whole for inspection; for example, at leastthe electron beam optics position may be changed during the period whilethe object is moved to place a new inspection area within the die orfield to within the field of view of the associated electron beamcolumn. In an embodiment, the adjustment may be to account for errors inthe location of an electron beam column or its electron beam optics,which may arise from movement by, for example, actuator 620 and/oractuator 840, 850. In that case, in an embodiment, actuator 860 can movethe electron beam optics, for example, in direction 1010, to put theelectron beam optics in a desired position. In an embodiment, theadjustment may be, e.g., in a direction 1000, to account formisalignment with an area having a suspected defected as describedhereafter.

Similarly, the electron beam column 600 may be slightly adjusted 1000,1010 in position (e.g., horizontal position or tilt) using actuator 840,850. Such adjustment may occur while the object is moved relative to theelectron beam columns during the processing the object as a whole forinspection; for example, an individual electron beam column position maybe changed during the period while the object is moved to place a newinspection area within the die or field to within the field of view ofthe associated electron beam column. In an embodiment, the adjustmentmay be to account for errors in the location of an electron beam column,which may arise from movement by, for example, actuator 620 and/oractuator 840, 850. In that case, in an embodiment, actuator 840, 850 canmove the electron beam column, for example, in direction 1010, to putthe electron beam column (and its electron beam optics) in a desiredposition. In an embodiment, the adjustment may be, e.g., in a direction1000, to account for misalignment with an area having a suspecteddefected as described hereafter.

The adjustment as described above may be based on sensor data asdescribed hereafter and/or based on other measured data, such asalignment, overlay and mask registration data that helps locate where apattern feature of a pattern is located in the corresponding die orfield at the object, i.e., computationally predict a shift of thepattern feature on the object.

In an embodiment, electron beam column optionally comprises an actuator860 to move the electron beam optics 800 and/or electron beam processingequipment 810. The actuator 860 may enable fine movement compared to therelatively coarse movement provided by actuator portion 840 and/or 850.In an embodiment, the actuator 860 comprises a linear motor and/or apiezoelectric actuator. In an embodiment, the actuator 860 can move theelectron beam optics 800 and/or electron beam processing equipment 810in up to and including 6 degrees of freedom

In an embodiment, the electron beam column comprises an optional sensor820. In an embodiment, the sensor 820 provides radiation 830 (e.g.,light) to determine the position of the electron beam column relative tothe object. For example, the sensor 820 can determine a distance fromthe electron beam column to the object and/or determine a tilt betweenthe electron beam column and the object. Additionally or alternatively,in an embodiment, the sensor 820 measures an alignment mark or othertarget on the object to determine a relative position between theelectron beam column and a location on the object. Such information canbe supplied to the actuator system for moving the electron beam column(e.g., actuator portion 840 and/or 850) and/or electron beam optics(e.g., actuator 860) to enable control of the position of the electronbeam column and/or electron beam optics respectively, and/or to theoptics/structure of the electron beam processing equipment 810 formoving the beam to enable control of the position of the electron beam.

A smaller field of view decreases the pixel size, enabling detection ofsmaller pattern excursions, but requires more accurate alignment. So,provided the columns are well aligned by high-precision mechatronics orby using, for example, sensors, a smaller field of view can be used,yielding higher resolution and higher inspection speed.

Further, in an embodiment, there is provided a synergistic combinationof computational defect prediction with parallel inspection using aplurality of electron beam columns arranged at dies or fields asdiscussed above to enable increased throughput, accuracy and/orefficiency by inspecting less than the entire area of the respectivedies or fields. For example, computational defect prediction couldreduce the size of the area to be inspected by ˜2-3 orders and soprovide significantly faster inspection to identify potentiallydefective features on the object, compared to a single-beam electronbeam inspection apparatus or a multi-beam electron beam inspectionapparatus. For example, a single-beam electron beam apparatus would takea significant amount of time to scan a die or field, let alone all thedies or fields on the object, and moreover spend much of that timeinspecting pattern features that are fine. Further, a multi-beamelectron beam apparatus would have a relatively large, combined field ofview across the several beams. But, an area where a defect is likely tooccur (˜0.5-3 μm²) is already smaller than the field of view of a singlebeam (˜100 μm²), let alone a combined field of view of 10,000 μm² (e.g.,10×10 array of beams). So, only one or a couple of expected defectswould fall within the combined field of view and so a multi-beamelectron beam apparatus would not significantly speed-up inspection ofdefects.

The improvement in, e.g., throughput can be achieved because of theinsight that many defects are systematic and pattern-dependent (e.g., ona semiconductor wafer) and so the likelihood is fairly high thatcomputational defect prediction will identify defects in the same orsimilar positions in each die or field (except perhaps for the edge of asemiconductor wafer). Thus, if the electron beam columns are pre-alignedwith the dies or fields, a single relative movement between the group ofelectron beam columns and the object will place respective areas havingone or more predicted defects within the field of view of all, amajority, or many of the electron beam columns, thus enabling parallelinspection. In other words, the electron beam columns can be keptfundamentally stationary relative to each other during and betweeninspections so that a relative movement between the collection ofelectron beam columns and the object can in parallel locate the impactpoint of each electron beam at a respective area in each die or fieldhaving one or more potential defects. In this manner, the electron beamscan be quickly in parallel located at potentially defective areas.Moreover, less than the entire area of each die or field would need tobe inspected with an electron beam in order to achieve significant speedand throughput gains.

Thus, in an embodiment, there is provided a two-dimensional array ofminiature electron beam columns, with at least one column per object dieor field, that inspect less than the entire area of each respective dieor field based on identification of one or more areas in the respectivedie or field having a potential for one or more defects. In anembodiment, the one or more defects are computationally predicted by,e.g., simulation. In an embodiment, the electron beam columns areadjustable in pitch in at least the X and/or Y direction to enablealignment with dies or fields.

As mentioned above, in an embodiment, an entire die or field of theobject is not inspected. In an embodiment, the majority of dies orfields of the object are not inspected. In an embodiment, the entirepatterned part of the object is not inspected. In an embodiment, an areahaving a potential defect can be termed a hotspot. A hotspot is areacomprising one or more pattern features that can have a tendency to havea defect in their patterning. So, in an embodiment, the inspectionsystem can inspect discrete hotspots within a die or field. In anembodiment, a hotspot area measures 2 microns square or less (e.g.,1.41×1.41 microns, 1×1 microns or 0.77×0.77 microns). A die or field mayhave a plurality of hotspot areas. In many cases, the hotspot areas willbe discrete within the die or field. In an embodiment, a plurality ofhotspot areas may be located adjacent each other such that they overlapor connect, thus forming a contiguous group of hotspot areas. So, byinspecting only the hotspots, electron beam object inspection throughputcan be increased by about two orders of magnitude (˜100 times).

In an embodiment, areas of predicted defects (e.g., hotspots) can beidentified using any suitable method from a pattern (e.g., a pattern ofor for a patterning device). For example, areas of predicted defects maybe identified by analyzing at least a part of the pattern using anempirical model or a computational model. In an empirical model, images(e.g., resist image, optical image, etch image) of the pattern are notsimulated; instead, the empirical model predicts defects or probabilityof defects based on correlations between processing parameters,parameters of the pattern, and the defects. For example, an empiricalmodel may be a classification model or a database of patterns prone todefects. In a computational model, a portion or a characteristic of thepattern as printed is calculated or simulated, and defects areidentified based on the portion or the characteristic. For example, aline pull back defect may be identified by finding a line end too faraway from its desired location; a bridging defect may be identified byfinding a location where two lines undesirably join; an overlappingdefect may be identified by finding that two features on separate layersundesirably overlap or undesirably do not overlap. In another example,areas of predicted defects may be determined experimentally, such as byfocus exposure matrix substrate qualification or a suitable metrologytool.

In an embodiment, one or more areas comprising one or more predicteddefects are determined based on a design rule check. Design rules caninclude specification of a minimum spacing between two features, aminimum dimension of a feature, etc. Thus, the pattern to be printed canbe checked for compliance with design rules and those portions of thepattern failing to comply or close failing to comply with a design rulecan be identified (and experimentally tested by patterning ofsubstrates). Such portions can be considered as care areas, which areareas of the pattern (die) having higher sensitivity to processexcursions (and thus having a higher likelihood for a defect).

In an embodiment, one or more areas comprising one or more predicteddefects are determined based on one or more patterning processmathematical models at nominal conditions (this can be for the fullpattern (full chip) or for a library of known problem pattern features).Portions of the pattern (or pattern features) can be identified thatprint poorly even under nominal conditions (and thus have a higherlikelihood for a defect). Such portions can be considered as carepatterns.

In an embodiment, one or more areas comprising one or more predicteddefects are determined by simulation using one or more patterningprocess mathematical models that use design data of the pattern and datafrom the patterning process. For example, the process described inrespect of FIG. 13 can be used to derive the existence of areas ofpredicted defects, as well as determine their location in a respectivefield or die. In an embodiment, the simulation process described inrespect of FIG. 13 can be performed for varying different excursionsfrom the nominal conditions to identify those patterns (hotspots) withhigher sensitivity to process excursions (and thus having a higherlikelihood for a defect). Optionally, the simulation can be furtheraugmented with measured data for or from one or more substrates exposedwith the pattern. For example, a measured focus map for one or moresubstrates may identify the focus for dies or fields (or portionsthereof) and based on the focus map, only those dies or fields (orportions thereof) with a de-focus exceeding a threshold are inspected;this may, however, yield a lower capture rate since it would not checkall the possibly sensitive areas across all dies or fields.

In an embodiment, a hotspot may be identified by evaluating the processwindows of features in a region of a pattern. A process window for afeature of a pattern is a space of processing parameters (e.g., dose andfocus) under which the feature will be produced within specification ona substrate. Examples of pattern specifications that relate to potentialdefects include checks for necking, line pull back, line thinning, CD,edge placement, overlapping, resist top loss, resist undercut andbridging. Various features in the region of the pattern may havedifferent process windows. The combined process window of all thefeatures in the region may be obtained by merging (e.g., overlapping)the process window of each individual feature in that region. Theboundary of the process window of all the features contains boundariesof the process windows of some of the individual features. In otherwords, these individual features limit the combined process window ofall the features in the region. These features can be referred to as“hotspots.” Thus, when evaluating which areas of an object are to beinspected, it is possible and economical to focus on the hotspots whichare effectively those pattern features that do not fall within thecombined process window of the particular region. When a hotspot in theregion as printed on the substrate is not defective, it is most likelythat the all the features in the region are not defective. It ispossible to determine and/or compile process windows of the hotspotsinto a map, based on hotspot locations and process windows of individualhotspots—i.e. determine process windows as a function of location. Thisprocess window map may characterize the layout-specific sensitivitiesand processing margins of the pattern. In an embodiment, the ASMLTachyon FEM model software may be used to identify hotspots.

In an embodiment, only the one or more care areas, care patterns orhotspots per die or field are inspected using the multi-electron beamcolumn apparatus described herein. In an embodiment, the care areas,care patterns or hotspots are smaller than the field of view of theelectron beam column. In an embodiment, the care areas, care patterns orhotspots have area of between 0.05-10 μm², 0.1-5 μm², or 0.5-2 μm².

Referring to FIGS. 11A, 11B and 11C, an embodiment of a technique ofusing bright-field inspection is highly schematically shown using careareas 1100. In FIG. 11A, care areas 1100 have been determined for eachfield or die 120 of the object 100. The care areas 1100 can bedetermined as described above. Then, referring to FIG. 11B, bright-fieldinspection is used to inspect the care area to identify suspecteddefects 410. The care areas are typically inspected by providingrelative movement between the object and the bright-field beam so thatall the care areas are inspected. The bright-field inspection may not becapable of definitively identifying whether the suspected defects 410are actual defects because the features or defects may be too small.Electron beam defect review is then performed at FIG. 11C to identifywhich of the suspected defects 410 are actual defects and optionallycharacterize the defects (e.g., provide a CD value). As shown in thisexample, the number of actual defects in FIG. 11C is less than thesuspected defects in FIG. 11B. As can be seen, this process can be, forexample, quite time-consuming.

Referring to FIGS. 12A and 12B, an embodiment of electron beaminspection using a plurality of electron beam columns and predictedhotspots is highly schematically illustrated. In FIG. 12A, one or morehotspots 410 for each field or die 120 on the object 100 is determinedusing techniques as described above. Typically, there will be aplurality of hotspots per field or die. Further, as shown in FIG. 12A,many of the hotspots may occur in the same or similar locations in eachfield or die. In an embodiment, a margin may be added to each identifiedhotspot location to help ensure that the respective electron beam has ahigh likelihood of inspecting whether the hotspot has the predicteddefect or not. Further, the threshold for identifying a hotspot may belower for defect inspection than used for controlling, designing, etc. apatterning process. This is so that even “marginal” hotspots areevaluated to help ensure more completeness. For example, to balanceproper capture rate against risk of inaccurate simulation, there wouldbe, in an embodiment, more predicted hotspots than bright-fieldidentified suspected defects.

Further, as shown in FIG. 12A, the fields of view 500 of the electronbeam columns 600 per field or die are shown. In this example, each ofthe fields of view 500 aligns with an area having one or more hotspots.If one or more of those fields of view 500 did not align with areahaving one or more hotspots, the process could still proceed exceptthose fields of view wouldn't be “productive” and further inspectingmight be needed to cover areas that couldn't be simultaneously inspectedby all or a majority of the electron beams. In an embodiment, a slightadjustment could be made to those one or more fields of view 500 thatare not aligned with an area having one or more hotspots as describedwith respect to FIG. 10.

Then, relative motion is performed between the electron beam columns andthe object at FIGS. 12A and 12B so that the respective fields of vieware aligned on all the hotspot areas so that electron beam inspectioncan be performed. Subsequently or concurrently, the results of electronbeam inspection are evaluated to identify whether a hotspot is defectiveor not and optionally characterize the defects (e.g., provide a CDvalue). As shown in this example, the number of actual defects in FIG.12B is less than the hotspots in FIG. 12A.

While FIGS. 12A and 12B were described in respect of hotspots, the sameprocess can be used care areas and/or care patterns. However, the careareas and/or care patterns may be larger in area than hotspot and so maybe more time-consuming to inspect, although there will be an increase inthroughput in inspecting those using a plurality of electron beamcolumns compared to the process of FIGS. 11A-C.

Thus, the techniques described herein could replace bright-fieldinspection, including during process ramp and including bright-fieldthat uses computed areas of predicted defects (such as care areas orcare patterns). To enable high throughput, the total area of predictedhotspots could be ˜2-3 orders smaller than total care areas estimatedfor bright-field inspection. Further, a plurality of electron beamcolumns arranged to measure in parallel could inspect all predictedhotspots ˜1-2 orders faster than a single electron beam defect reviewidentifies actual defects as shown in FIG. 11C. 30, 40, 60, 70, 80, 90,100, 110 or more electron beam columns would enable such speed-up.

The results of the inspection can be used in various ways. For example,the pattern feature associated with a hotspot identified as defectivecan be, for example, removed or corrected in the design process, haveits patterning compensated for by changing a process parameter, etc. Ahotspot identified as not being defective can be used to tune the model.A contour of the hotspot (whether defective or not) can be used tocalibrate the model, i.e., the contour produced by the model can becompared with the measured contour and then the model updatedaccordingly.

While the discussion above has mostly focused on inspection of asubstrate in the form of, e.g., a semiconductor wafer, the apparatusesand methods herein can be applied to a patterning device (e.g., a maskor reticle). That is the inspected object can be a patterning device.Accordingly, the number of electron beam columns may be appropriatelyselected.

In an embodiment, a patterning device is corrected based on a parameterderived from the detected electrons by the electron beam columns. In anembodiment, the correction is made where the inspected object is thepatterning device itself or a similar version, or copy, of thepatterning device. In an embodiment, the correction is made where theinspected object is a substrate onto which a pattern is transferred(e.g., a semiconductor substrate). In an embodiment,

In an embodiment, the apparatuses and methods described herein areadapted to additionally, or alternatively, enable patterning devicerepair. That is, in an embodiment, a multiple electron beam columnapparatus is provided that enables repair in parallel at multiple diesor fields. The electron beams provided by the electron beam columns canenable the repair (and optionally may be used for detecting as describedherein). In an embodiment, the electron beams enable removal of materialfrom the patterning device. If the electron beam columns enablemeasurement, then the power of the electron beams can be adjustedbetween measurement and repair. In an embodiment, to enable repair, amaterial may be provided to interact with the electron beams. In anembodiment, an outlet 700 is provided to supply a precursor fluid (e.g.,a gas). The fluid can enable deposition of material when used incombination with the electron beams. In an embodiment, an ion supplydevice is used in place of, or in combination, with the electron beamcolumns to enable the repair. In an embodiment, the ion supply devicesare configured to provide a metal ion. Details of repair of a patterningdevice can be found in, for example, U.S. Patent Application PublicationNo. 2004-0151991 and U.S. Pat. No. 7,916,930, which are incorporatedherein in their entirety by reference.

Further, while the discussion above has mostly focused on inspectionusing electron beam columns, a different inspection apparatus than anelectron beam column could be used in the apparatuses and methodsdescribed herein. That is, each of the plurality of electron beamcolumns can be replaced by, or supplemented with, a different inspectionapparatus. Other than the difference in the type of inspectionapparatus, the apparatuses and methods described herein would befundamentally the same except modified to accommodate the differentinspection apparatuses.

In an embodiment, there is provided an electron beam inspectionapparatus to inspect an object comprising a plurality of dies or fields,the apparatus comprising: a plurality of electron beam columns, eachelectron beam column configured to provide an electron beam and detectscattered or secondary electrons from the object, each electron beamcolumn arranged to inspect a different respective field or dieassociated with the electron beam column; and a non-transitory computerprogram product comprising machine-readable instructions, at least someof the instructions configured to cause relative movement between theobject and the electron beam columns such that each of the electronbeams inspects an area of its respective field or die less than theentire area of the respective field or die.

In an embodiment, at least one of the areas comprises an identifiedhotspot. In an embodiment, at least some of the instructions areconfigured to determine the existence and/or location of the hotspot. Inan embodiment, at least some of the instructions are configured toidentify the hotspot by simulation. In an embodiment, the plurality ofelectron beam columns is arranged in a two-dimensional array andcomprises at least 30 electron beam columns. In an embodiment, theapparatus further comprises an actuator system configured to move one ormore of the electron beam columns relative to another one or more of theelectron beam columns. In an embodiment, at least some of theinstructions are configured to cause a plurality of the electron beamsto impinge respective areas of their respective fields or dies at a sametime.

In an embodiment, there is provided an electron beam inspectionapparatus, comprising: a plurality of electron beam columns, eachelectron beam column configured to provide an electron beam and detectscattered or secondary electrons from the object, each electron beamcolumn arranged to inspect an area of a different respective field ordie associated with the electron beam column; and an actuator systemconfigured to move one or more of the electron beam columns relative toanother one or more of the electron beam columns.

In an embodiment, the actuator system is configured to change a pitch ofthe plurality of electron beam columns. In an embodiment, the pluralityof electron beam columns is arranged in a two-dimensional array and theactuator system is configured to change a position of an electron beamcolumn in a first direction and in a second direction substantiallyorthogonal to the first direction. In an embodiment, each electron beamcolumn is movable independently of the other electron beam columns. Inan embodiment, the plurality of electron beam columns comprises at least30 electron beam columns. In an embodiment, the apparatus furthercomprises a non-transitory computer program product comprisingmachine-readable instructions configured to cause relative movementbetween the object and the electron beam columns such that each of theelectron beams inspects an area of its respective field or die less thanthe entire area of the respective field or die. In an embodiment, atleast one of the areas comprises an identified hotspot. In anembodiment, the apparatus comprises a non-transitory computer programproduct comprising machine-readable instructions configured to determinethe existence and/or location of the hotspot. In an embodiment, theapparatus comprises a non-transitory computer program product comprisingmachine-readable instructions configured to identify the hotspot bysimulation.

In an embodiment, there is provided a method of electron beam inspectionof an object comprising a plurality of dies or fields, the methodcomprising: having a plurality of electron beam columns, each electronbeam column configured to provide an electron beam and detect scatteredor secondary electrons from the object and each electron beam columnarranged to inspect a different respective field or die associated withthe electron beam column; causing relative movement between the objectand the plurality of electron beam columns such that each of theelectron beams inspects an area of its respective field or die less thanthe entire area of the respective field or die; providing the electronbeams onto the object from the electron beam columns; and detectingscattered or secondary electrons from the object using the electron beamcolumns.

In an embodiment, at least one of the areas comprises an identifiedhotspot. In an embodiment, the method further comprises determining, bya computer, the existence and/or location of the hotspot. In anembodiment, the method further comprises identifying the hotspot bycomputer simulation. In an embodiment, the plurality of electron beamcolumns is arranged in a two-dimensional array and comprises at least 30electron beam columns. In an embodiment, the method further comprisesmoving one or more of the electron beam columns relative to another oneor more of the electron beam columns using an actuator. In anembodiment, the object comprises a patterning device or a semiconductorwafer. In an embodiment, the method further comprises repairing theobject or a patterning device, based on a parameter derived from thedetected electrons from the object.

In an embodiment, there is provided a method of electron beaminspection, the method comprising: having a plurality of electron beamcolumns, each electron beam column configured to provide an electronbeam and detect scattered or secondary electrons from an object and eachelectron beam column arranged to inspect an area of a differentrespective field or die associated with the electron beam column; andmoving one or more of the electron beam columns relative to another oneor more of the electron beam columns using an actuator system.

In an embodiment, the method comprises changing a pitch of the pluralityof electron beam columns. In an embodiment, the plurality of electronbeam columns is arranged in a two-dimensional array and changing aposition of an electron beam column in a first direction and in a seconddirection substantially orthogonal to the first direction. In anembodiment, each electron beam column is movable independently of theother electron beam columns. In an embodiment, the plurality of electronbeam columns comprises at least 30 electron beam columns. In anembodiment, the method further comprises causing relative movementbetween the object and the electron beam columns such that each of theelectron beams inspects an area of its respective field or die less thanthe entire area of the respective field or die. In an embodiment, atleast one of the areas comprises an identified hotspot. In anembodiment, the method further comprises determining, by a computer, theexistence and/or location of the hotspot. In an embodiment, the methodfurther comprises identifying the hotspot by computer simulation. In anembodiment, the object comprises a patterning device or a semiconductorwafer. In an embodiment, the method further comprises repairing theobject or a patterning device, based on a parameter derived from thedetected electrons from the object.

In an embodiment, there is provided an electron beam inspectionapparatus, the apparatus comprising: a plurality of electron beamcolumns, each electron beam column configured to provide an electronbeam and detect scattered or secondary electrons from an object; and anactuator system configured to move one or more of the electron beamcolumns relative to another one or more of the electron beam columns,the actuator system comprising a plurality of first movable structuresat least partly overlapping a plurality of second movable structures,the first and second movable structures supporting the plurality ofelectron beam columns.

In an embodiment, one or more of the first movable structures is movablerelative to another one or more of the first movable structures and/orone or more of the second movable structures is movable relative toanother one or more of the second movable structures. In an embodiment,an electron beam column of the electron beam columns is connected to acolumn structure having a first component thereof that physically andmovably engages with a first movable structure of the first movablestructures and a second component thereof that physically and movablyengages with a second movable structure of the second movablestructures. In an embodiment, the first component is located within thefirst movable structure and/or the second component is located withinthe second movable structure. In an embodiment, the apparatus furthercomprises a first brake configured to engage with the first movablestructure in order to hold the column structure in fixed position inrelation to the first movable structure and/or a second brake configuredto engage with the second movable structure in order to hold the columnstructure in fixed position in relation to the second movable structure.In an embodiment, the apparatus comprises the first brake and the secondbrake and further comprises a control system configured to cause thefirst brake to be engaged, while the second brake is disengaged, toallow the second movable structure to move the electron beam column ofthe column structure and to cause the second brake to be engaged, whilethe first brake is disengaged, to allow the first movable structure tomove the electron beam column of the column structure. In an embodiment,one or more the electron beam columns is located to a side of anadjacent first movable structure and/or second movable structure and ina gap between adjacent first movable structures and/or adjacent secondmovable structures. In an embodiment, at least one of the electron beamcolumns is connected to a short stroke actuator having a movement rangesmaller than a movement range of the first and second movablestructures. In an embodiment, the apparatus further comprises aplurality of sensors, each configured to measure a distance to enabledetermination of a position of an associated electron beam column inrespect of an adjacent electron beam column. In an embodiment, eachelectron beam column is arranged to inspect an area of a differentrespective field or die of the object associated with the electron beamcolumn. In an embodiment, the apparatus further comprises anon-transitory computer program product comprising machine-readableinstructions, at least some of the instructions configured to causerelative movement between the object and the electron beam columns suchthat each of the electron beams inspects an area of its respective fieldor die less than the entire area of the respective field or die.

In an embodiment, there is provided a method of electron beaminspection, the method comprising: having a plurality of electron beamcolumns, each electron beam column configured to provide an electronbeam and detect scattered or secondary electrons from an object; movingone or more of the electron beam columns relative to another one or moreof the electron beam columns using an actuator system, the actuatorsystem comprising a plurality of first movable structures at leastpartly overlapping a plurality of second movable structures, the firstand second movable structures supporting the plurality of electron beamcolumns; providing the electron beams onto the object from the electronbeam columns; and detecting scattered or secondary electrons from theobject using the electron beam columns.

In an embodiment, the method comprises moving one or more of the firstmovable structures relative to another one or more of the first movablestructures and/or moving one or more of the second movable structuresrelative to another one or more of the second movable structures. In anembodiment, an electron beam column of the electron beam columns isconnected to a column structure having a first component thereof and asecond component thereof and the method further comprises moving thefirst component while in physical engagement with a first movablestructure of the first movable structures and moving the secondcomponent while in physical engagement with a second movable structureof the second movable structures. In an embodiment, the first componentis located within the first movable structure and/or the secondcomponent is located within the second movable structure. In anembodiment, the method further comprises engaging a first brake with thefirst movable structure in order to hold the column structure in fixedposition in relation to the first movable structure and/or engaging asecond brake with the second movable structure in order to hold thecolumn structure in fixed position in relation to the second movablestructure. In an embodiment, the method comprises causing the firstbrake to be engaged, while the second brake is disengaged, to allow thesecond movable structure to move the electron beam column of the columnstructure and causing the second brake to be engaged, while the firstbrake is disengaged, to allow the first movable structure to move theelectron beam column of the column structure. In an embodiment, one ormore the electron beam columns is located to a side of an adjacent firstmovable structure and/or second movable structure and in a gap betweenadjacent first movable structures and/or adjacent second movablestructures. In an embodiment, the method further comprises moving atleast one of the electron beam columns using a short stroke actuatorhaving a movement range smaller than a movement range of the first andsecond movable structures. In an embodiment, the method furthercomprises using a plurality of sensors, each measuring a distance toenable determination of a position of an associated electron beam columnin respect of an adjacent electron beam column. In an embodiment, eachelectron beam column is arranged to inspect an area of a differentrespective field or die of the object associated with the electron beamcolumn. In an embodiment, the method further comprises causing relativemovement between the object and the electron beam columns such that eachof the electron beams inspects an area of its respective field or dieless than the entire area of the respective field or die. In anembodiment, the object comprises a patterning device or a semiconductorwafer. In an embodiment, the method further comprises repairing theobject or a patterning device, based on a parameter derived from thedetected electrons from the object.

In an embodiment, there is provided a patterning device repairapparatus, comprising: a plurality of beam columns, each beam columnconfigured to provide a beam of radiation, each beam column arranged torepair an area of a different respective field or die of a patterningdevice associated with the beam column using the respective beam ofradiation; and an actuator system configured to move one or more of thebeam columns relative to another one or more of the beam columns.

In an embodiment, each of the beam columns are further configured todetect scattered or secondary electrons from the patterning device. Inan embodiment, each beam column is arranged to inspect an area of adifferent respective field or die associated with the beam column. In anembodiment, the beam columns are respectively configured to provide anelectron beam. In an embodiment, the beam columns are respectivelyconfigured to provide an ion beam.

In association with an imaging apparatus such as a SEM, an embodimentmay include a computer program containing one or more sequences ofmachine-readable instructions that enable practice of a method asdescribed herein. This computer program may be included, for example,with or within the imaging apparatus of FIG. 3 and/or with or within thecontrol unit LACU of FIG. 2. There may also be provided a data storagemedium (e.g., semiconductor memory, magnetic or optical disk) havingsuch a computer program stored therein. Where an existing apparatus, forexample of the type shown in FIGS. 1-3, is already in production and/orin use, an embodiment can be implemented by the provision of updatedcomputer program products for causing a processor of the apparatus toperform a method as described herein.

An embodiment of the invention may take the form of a computer programcontaining one or more sequences of machine-readable instructionsdescribing a method as disclosed herein, or a data storage medium (e.g.semiconductor memory, magnetic or optical disk) having such a computerprogram stored therein. Further, the machine readable instruction may beembodied in two or more computer programs. The two or more computerprograms may be stored on one or more different memories and/or datastorage media.

Any controllers described herein may each or in combination be operablewhen the one or more computer programs are read by one or more computerprocessors located within at least one component of the lithographicapparatus. The controllers may each or in combination have any suitableconfiguration for receiving, processing, and sending signals. One ormore processors are configured to communicate with the at least one ofthe controllers. For example, each controller may include one or moreprocessors for executing the computer programs that includemachine-readable instructions for the methods described above. Thecontrollers may include data storage medium for storing such computerprograms, and/or hardware to receive such medium. So the controller(s)may operate according the machine readable instructions of one or morecomputer programs.

Although specific reference may have been made above to the use ofembodiments in the context of optical lithography, it will beappreciated that an embodiment of the invention may be used in otherapplications, for example imprint lithography, and where the contextallows, is not limited to optical lithography. In imprint lithography, atopography in a patterning device defines the pattern created on asubstrate. The topography of the patterning device may be pressed into alayer of resist supplied to the substrate whereupon the resist is curedby applying electromagnetic radiation, heat, pressure or a combinationthereof. The patterning device is moved out of the resist leaving apattern in it after the resist is cured.

Further, although specific reference may be made in this text to the useof lithographic apparatus in the manufacture of ICs, it should beunderstood that the lithographic apparatus described herein may haveother applications, such as the manufacture of integrated opticalsystems, guidance and detection patterns for magnetic domain memories,flat-panel displays, liquid-crystal displays (LCDs), thin film magneticheads, etc. The skilled artisan will appreciate that, in the context ofsuch alternative applications, any use of the terms “wafer” or “die”herein may be considered as synonymous with the more general terms“substrate” or “target portion”, respectively. The substrate referred toherein may be processed, before or after exposure, in for example atrack (a tool that typically applies a layer of resist to a substrateand develops the exposed resist), a metrology tool and/or an inspectiontool. Where applicable, the disclosure herein may be applied to such andother substrate processing tools. Further, the substrate may beprocessed more than once, for example in order to create a multi-layerIC, so that the term substrate used herein may also refer to a substratethat already contains multiple processed layers.

The terms “radiation” and “beam” used herein encompass all types ofelectromagnetic radiation, including ultraviolet (UV) radiation (e.g.having a wavelength of or about 365, 355, 248, 193, 157 or 126 nm) andextreme ultra-violet (EUV) radiation (e.g. having a wavelength in therange of 5-20 nm), as well as particle beams, such as ion beams orelectron beams.

The term “lens”, where the context allows, may refer to any one orcombination of various types of optical components, includingrefractive, reflective, magnetic, electromagnetic and electrostaticoptical components.

The term “optimizing” and “optimization” as used herein refers to ormeans adjusting a patterning process apparatus, one or more steps of apatterning process, etc. such that results and/or processes ofpatterning have more desirable characteristics, such as higher accuracyof transfer of a design layout on a substrate, a larger process window,etc. Thus, the term “optimizing” and “optimization” as used hereinrefers to or means a process that identifies one or more values for oneor more parameters that provide an improvement, e.g. a local optimum, inat least one relevant metric, compared to an initial set of one or morevalues for those one or more parameters. “Optimum” and other relatedterms should be construed accordingly. In an embodiment, optimizationsteps can be applied iteratively to provide further improvements in oneor more metrics.

The invention may further be described using the following clauses:

1. An electron beam inspection apparatus to inspect an object comprisinga plurality of dies or fields, the apparatus comprising:

a plurality of electron beam columns, each electron beam columnconfigured to provide an electron beam and detect scattered or secondaryelectrons from the object, each electron beam column arranged to inspecta different respective field or die associated with the electron beamcolumn; and

a non-transitory computer program product comprising machine-readableinstructions, at least some of the instructions configured to causerelative movement between the object and the electron beam columns suchthat each of the electron beams inspects an area of its respective fieldor die less than the entire area of the respective field or die.2. The apparatus of clause 1, wherein at least one of the areascomprises an identified hotspot.3. The apparatus of clause 2, wherein at least some of the instructionsare configured to determine the existence and/or location of thehotspot.4. The apparatus of clause 2 or clause 3, wherein at least some of theinstructions are configured to identify the hotspot by simulation.5. The apparatus of any of clauses 1 to 4, wherein the plurality ofelectron beam columns are arranged in a two-dimensional array andcomprises at least 30 electron beam columns.6. The apparatus of any of clauses 1 to 5, further comprising anactuator system configured to move one or more of the electron beamcolumns relative to another one or more of the electron beam columns.7. The apparatus of any of clauses 1 to 6, wherein at least some of theinstructions are configured to cause a plurality of the electron beamsto impinge respective areas of their respective fields or dies at a sametime.8. An electron beam inspection apparatus, comprising:

a plurality of electron beam columns, each electron beam columnconfigured to provide an electron beam and detect scattered or secondaryelectrons from an object, each electron beam column arranged to inspectan area of a different respective field or die associated with theelectron beam column; and

an actuator system configured to move one or more of the electron beamcolumns relative to another one or more of the electron beam columns.

9. The apparatus of clause 8, wherein the actuator system is configuredto change a pitch of the plurality of electron beam columns.10. The apparatus of clause 8 or clause 9, wherein the plurality ofelectron beam columns is arranged in a two-dimensional array and theactuator system is configured to change a position of an electron beamcolumn in a first direction and in a second direction substantiallyorthogonal to the first direction.11. The apparatus of any of clauses 8 to 10, wherein each electron beamcolumn is movable independently of the other electron beam columns.12. The apparatus of any of clauses 8 to 11, wherein the plurality ofelectron beam columns comprises at least 30 electron beam columns.13. The apparatus of any of clauses 8 to 12, further comprising anon-transitory computer program product comprising machine-readableinstructions configured to cause relative movement between the objectand the electron beam columns such that each of the electron beamsinspects an area of its respective field or die less than the entirearea of the respective field or die.14. The apparatus of any of clauses 8 to 13, wherein at least one of theareas comprises an identified hotspot.15. The apparatus of clause 14, comprising a non-transitory computerprogram product comprising machine-readable instructions configured todetermine the existence and/or location of the hotspot.16. The apparatus of clause 14 or clause 15, comprising a non-transitorycomputer program product comprising machine-readable instructionsconfigured to identify the hotspot by simulation.17. A method of electron beam inspection of an object comprising aplurality of dies or fields, the method comprising:

having a plurality of electron beam columns, each electron beam columnconfigured to provide an electron beam and detect scattered or secondaryelectrons from the object and each electron beam column arranged toinspect a different respective field or die associated with the electronbeam column;

causing relative movement between the object and the plurality ofelectron beam columns such that each of the electron beams inspects anarea of its respective field or die less than the entire area of therespective field or die;providing the electron beams onto the object from the electron beamcolumns; and detecting scattered or secondary electrons from the objectusing the electron beam columns.18. The method of clause 17, wherein at least one of the areas comprisesan identified hotspot.19. The method of clause 18, further comprising determining, by acomputer, the existence and/or location of the hotspot.20. The method of clause 18 or clause 19, further comprising identifyingthe hotspot by computer simulation.21. The method of any of clauses 17 to 20, wherein the plurality ofelectron beam columns are arranged in a two-dimensional array andcomprises at least 30 electron beam columns.22. The method of any of clauses 17 to 21, further comprising moving oneor more of the electron beam columns relative to another one or more ofthe electron beam columns using an actuator.23. The method of any of clauses 17 to 22, wherein the object comprisesa patterning device or a semiconductor wafer.24. The method of any of clauses 17 to 23, further comprising repairingthe object or a patterning device, based on a parameter derived from thedetected electrons from the object.25. A method of electron beam inspection, the method comprising:

having a plurality of electron beam columns, each electron beam columnconfigured to provide an electron beam and detect scattered or secondaryelectrons from an object and each electron beam column arranged toinspect an area of a different respective field or die of the objectassociated with the electron beam column; and

moving one or more of the electron beam columns relative to another oneor more of the electron beam columns using an actuator system.

26. The method of clause 25, comprising changing a pitch of theplurality of electron beam columns.27. The method of clause 25 or clause 26, wherein the plurality ofelectron beam columns is arranged in a two-dimensional array andchanging a position of an electron beam column in a first direction andin a second direction substantially orthogonal to the first direction.28. The method of any of clauses 25 to 27, wherein each electron beamcolumn is movable independently of the other electron beam columns.29. The method of any of clauses 25 to 28, wherein the plurality ofelectron beam columns comprises at least 30 electron beam columns.30. The method of any of clauses 25 to 28, further comprising causingrelative movement between the object and the electron beam columns suchthat each of the electron beams inspects an area of its respective fieldor die less than the entire area of the respective field or die.31. The method of any of clauses 25 to 30, wherein at least one of theareas comprises an identified hotspot.32. The method of clause 31, further comprising determining, by acomputer, the existence and/or location of the hotspot.33. The method of clause 31 or clause 32, further comprising identifyingthe hotspot by computer simulation.34. The method of any of clauses 25 to 33, wherein the object comprisesa patterning device or a semiconductor wafer.35. The method of any of clauses 25 to 34, further comprising repairingthe object or a patterning device, based on a parameter derived from thedetected electrons from the object.36. An electron beam inspection apparatus, the apparatus comprising:

a plurality of electron beam columns, each electron beam columnconfigured to provide an electron beam and detect scattered or secondaryelectrons from an object; and

an actuator system configured to move one or more of the electron beamcolumns relative to another one or more of the electron beam columns,the actuator system comprising a plurality of first movable structuresat least partly overlapping a plurality of second movable structures,the first and second movable structures supporting the plurality ofelectron beam columns.37. The apparatus of clause 36, wherein one or more of the first movablestructures is movable relative to another one or more of the firstmovable structures and/or one or more of the second movable structuresis movable relative to another one or more of the second movablestructures.38. The apparatus of clause 36 or clause 37, wherein an electron beamcolumn of the electron beam columns is connected to a column structurehaving a first component thereof that physically and movably engageswith a first movable structure of the first movable structures and asecond component thereof that physically and movably engages with asecond movable structure of the second movable structures.39. The apparatus of clause 38, wherein the first component is locatedwithin the first movable structure and/or the second component islocated within the second movable structure.40. The apparatus of clause 38 or clause 39, further comprising a firstbrake configured to engage with the first movable structure in order tohold the column structure in fixed position in relation to the firstmovable structure and/or a second brake configured to engage with thesecond movable structure in order to hold the column structure in fixedposition in relation to the second movable structure.41. The apparatus of clause 40, comprising the first brake and thesecond brake and further comprising a control system configured to causethe first brake to be engaged, while the second brake is disengaged, toallow the second movable structure to move the electron beam column ofthe column structure and to cause the second brake to be engaged, whilethe first brake is disengaged, to allow the first movable structure tomove the electron beam column of the column structure.42. The apparatus of any of clauses 36 to 41, wherein one or more theelectron beam columns is located to a side of an adjacent first movablestructure and/or second movable structure and in a gap between adjacentfirst movable structures and/or adjacent second movable structures.43. The apparatus of any of clauses 36 to 42, wherein at least one ofthe electron beam columns is connected to a short stroke actuator havinga movement range smaller than a movement range of the first and secondmovable structures.44. The apparatus of any of clauses 36 to 43, further comprising aplurality of sensors, each configured to measure a distance to enabledetermination of a position of an associated electron beam column inrespect of an adjacent electron beam column.45. The apparatus of any of clauses 36 to 44, wherein each electron beamcolumn is arranged to inspect an area of a different respective field ordie of the object associated with the electron beam column.46. The apparatus of clause 45, further comprising a non-transitorycomputer program product comprising machine-readable instructions, atleast some of the instructions configured to cause relative movementbetween the object and the electron beam columns such that each of theelectron beams inspects an area of its respective field or die less thanthe entire area of the respective field or die.47. A method of electron beam inspection, the method comprising:

having a plurality of electron beam columns, each electron beam columnconfigured to provide an electron beam and detect scattered or secondaryelectrons from an object;

moving one or more of the electron beam columns relative to another oneor more of the electron beam columns using an actuator system, theactuator system comprising a plurality of first movable structures atleast partly overlapping a plurality of second movable structures, thefirst and second movable structures supporting the plurality of electronbeam columns;

providing the electron beams onto the object from the electron beamcolumns; and detecting scattered or secondary electrons from the objectusing the electron beam columns.48. The method of clause 47, comprising moving one or more of the firstmovable structures relative to another one or more of the first movablestructures and/or moving one or more of the second movable structuresrelative to another one or more of the second movable structures.49. The method of clause 47 or clause 48, wherein an electron beamcolumn of the electron beam columns is connected to a column structurehaving a first component thereof and a second component thereof andfurther comprising moving the first component while in physicalengagement with a first movable structure of the first movablestructures and moving the second component while in physical engagementwith a second movable structure of the second movable structures.50. The method of clause 49, wherein the first component is locatedwithin the first movable structure and/or the second component islocated within the second movable structure.51. The method of clause 49 or clause 50, further comprising engaging afirst brake with the first movable structure in order to hold the columnstructure in fixed position in relation to the first movable structureand/or engaging a second brake with the second movable structure inorder to hold the column structure in fixed position in relation to thesecond movable structure.52. The method of clause 51, comprising causing the first brake to beengaged, while the second brake is disengaged, to allow the secondmovable structure to move the electron beam column of the columnstructure and causing the second brake to be engaged, while the firstbrake is disengaged, to allow the first movable structure to move theelectron beam column of the column structure.53. The method of any of clauses 47 to 52, wherein one or more theelectron beam columns is located to a side of an adjacent first movablestructure and/or second movable structure and in a gap between adjacentfirst movable structures and/or adjacent second movable structures.54. The method of any of clauses 47 to 53, further comprising moving atleast one of the electron beam columns using a short stroke actuatorhaving a movement range smaller than a movement range of the first andsecond movable structures.55. The method of any of clauses 47 to 54, further comprising using aplurality of sensors, each measuring a distance to enable determinationof a position of an associated electron beam column in respect of anadjacent electron beam column.56. The method of any of clauses 47 to 55, wherein each electron beamcolumn is arranged to inspect an area of a different respective field ordie of the object associated with the electron beam column.57. The method of clause 56, further comprising causing relativemovement between the object and the electron beam columns such that eachof the electron beams inspects an area of its respective field or dieless than the entire area of the respective field or die.58. The method of any of clauses 47 to 57, wherein the object comprisesa patterning device or a semiconductor wafer.59. The method of any of clauses 47 to 58, further comprising repairingthe object or a patterning device, based on a parameter derived from thedetected electrons from the object.60. A patterning device repair apparatus, comprising:

a plurality of beam columns, each beam column configured to provide abeam of radiation, each beam column arranged to repair an area of adifferent respective field or die of a patterning device associated withthe beam column using the respective beam of radiation; and

an actuator system configured to move one or more of the beam columnsrelative to another one or more of the beam columns.

61. The apparatus of clause 60, wherein each of the beam columns arefurther configured to detect scattered or secondary electrons from thepatterning device.62. The apparatus of clause 61, wherein each beam column is arranged toinspect an area of a different respective field or die associated withthe beam column.63. The apparatus of any of clauses 60 to 62, wherein the beam columnsare respectively configured to provide an electron beam.64. The apparatus of any of clauses 60 to 62, wherein the beam columnsare respectively configured to provide an ion beam.

The descriptions above are intended to be illustrative, not limiting.Thus, it will be apparent to one skilled in the art that modificationsmay be made to the invention as described without departing from thescope of the claims set out below. For example, one or more aspects ofone or more embodiments may be combined with or substituted for one ormore aspects of one or more other embodiments as appropriate. Therefore,such adaptations and modifications are intended to be within the meaningand range of equivalents of the disclosed embodiments, based on theteaching and guidance presented herein. It is to be understood that thephraseology or terminology herein is for the purpose of description byexample, and not of limitation, such that the terminology or phraseologyof the present specification is to be interpreted by the skilled artisanin light of the teachings and guidance. The breadth and scope of theinvention should not be limited by any of the above-described exemplaryembodiments, but should be defined only in accordance with the followingclaims and their equivalents.

1.-15. (canceled)
 16. An electron beam inspection apparatus comprising:a plurality of electron beam columns arranged in an array of one or morerows and one or more columns, each electron beam column configured toprovide a multi-beam of electron beams to an object, the object having aplurality of separate fields or dies, each field or die having aboundary to enable separation of the object into pieces; and an actuatorsystem configured to move one or more of the electron beam columnsrelative to another one or more of the electron beam columns, whereineach electron beam column in a row in the array and in a column of thearray inspects a portion of the object and the actuator system isconfigured to move the one or more of the electron beam columns relativeto another so that each electron beam column is aligned with itsportion.
 17. The inspection apparatus of claim 16, wherein all opticalcomponents or structures of each electron beam column are electrostaticelectron-optical components or structures.
 18. The inspection apparatusof claim 16, wherein the portion is at least part of a die so that eachelectron beam column in a row in the array and in a column of the arrayinspects at least a portion of its at least part of a die.
 19. Theinspection apparatus of claim 18, wherein the columns are configured tobe at a distance apart corresponding to a distance between adjacent dieson the object.
 20. The inspection apparatus of claim 16, wherein eachcolumn comprises a detector configured to measure secondary or scatteredelectrons from the object.
 21. The inspection apparatus of claim 16,wherein the array is a two dimensional array.
 22. The inspectionapparatus of claim 16, wherein a selection of the plurality of separatefields or dies are inspected in parallel by a selection of the beams intheir respective fields of view, or wherein a selection of a pluralityof beams are projected at the object at a same time such that each beaminspects a respective field or die, such that each electron beam columnscans a same portion of its respective field or die at the same time.23. The inspection apparatus of claim 16, wherein the number of electronbeam columns corresponds to the number of fields or dies.
 24. Theinspection apparatus of claim 16, wherein the actuator is arranged tochange a pitch of at least two of the electron beam columns.
 25. Theinspection apparatus of claim 16, wherein each electron beam column hasan identical, or nearly identical, datapath.
 26. The inspectionapparatus of claim 16, wherein at least one of the electron beam columnsin a row or column has its position adjusted independent of one or moreother electron beam columns in that row or column.
 27. The inspectionapparatus of claim 16, wherein a portion of each field or die isinspected.
 28. An electron beam inspection apparatus comprising: aplurality of electron beam columns arranged in an array of one or morerows and one or more columns, each electron beam column configured toprovide a multi-beam of electron beams to an object, the object having aplurality of separate fields or dies, each field or die having aboundary to enable separation of the object into pieces; and an actuatorsystem configured to move one or more of the electron beam columnsrelative to another one or more of the electron beam columns, whereineach electron beam column is arranged to scan a same portion of arespective field or die at a same time when the electron beams arescanned relative to the object.
 29. The inspection apparatus of claim28, wherein each portion corresponds to a different die on the object.30. The inspection apparatus of claim 28, wherein all optical componentsor structures of each electron beam column are electrostaticelectron-optical components or structures.
 31. The inspection apparatusof claim 28, wherein the portion is at least part of a die so that eachelectron beam column in a row in the array and in a column of the arrayinspects at least a portion of its at least part of a die.
 32. Theinspection apparatus of claim 31, wherein the columns are configured tobe at a distance apart corresponding to a distance between adjacent dieson the object.
 33. The inspection apparatus of claim 28, wherein eachelectron beam column comprises a detector configured to measuresecondary or scattered electrons from the object.
 34. The inspectionapparatus of claim 28, wherein the array is a two dimensional array. 35.The inspection apparatus of claim 28, wherein the number of electronbeam columns corresponds to the number of fields or dies.
 36. Theinspection apparatus of claim 28, wherein the actuator is arranged tochange a pitch of at least two of the electron beam columns.
 37. Theinspection apparatus of claim 28, wherein each electron beam column hasan identical, or nearly identical, datapath.